/*
 * Copyright (C) the libgit2 contributors. All rights reserved.
 *
 * This file is part of libgit2, distributed under the GNU GPL v2 with
 * a Linking Exception. For full terms see the included COPYING file.
 */
module libgit2_d.diff;


private static import libgit2_d.buffer;
private static import libgit2_d.oid;
private static import libgit2_d.strarray;
private static import libgit2_d.types;

/**
 * @file git2/diff.h
 * @brief Git tree and file differencing routines.
 * @ingroup Git
 * @{
 */
extern (C):
nothrow @nogc:
public:

/**
 * Flags for diff options.  A combination of these flags can be passed
 * in via the `flags` value in the `git_diff_options`.
 */
enum git_diff_option_t
{
	/**
	 * Normal diff, the default
	 */
	GIT_DIFF_NORMAL = 0,

	/*
	 * Options controlling which files will be in the diff
	 */

	/**
	 * Reverse the sides of the diff
	 */
	GIT_DIFF_REVERSE = 1u << 0,

	/**
	 * Include ignored files in the diff
	 */
	GIT_DIFF_INCLUDE_IGNORED = 1u << 1,

	/**
	 * Even with GIT_DIFF_INCLUDE_IGNORED, an entire ignored directory
	 *  will be marked with only a single entry in the diff; this flag
	 *  adds all files under the directory as IGNORED entries, too.
	 */
	GIT_DIFF_RECURSE_IGNORED_DIRS = 1u << 2,

	/**
	 * Include untracked files in the diff
	 */
	GIT_DIFF_INCLUDE_UNTRACKED = 1u << 3,

	/**
	 * Even with GIT_DIFF_INCLUDE_UNTRACKED, an entire untracked
	 *  directory will be marked with only a single entry in the diff
	 *  (a la what core Git does in `git status`); this flag adds *all*
	 *  files under untracked directories as UNTRACKED entries, too.
	 */
	GIT_DIFF_RECURSE_UNTRACKED_DIRS = 1u << 4,

	/**
	 * Include unmodified files in the diff
	 */
	GIT_DIFF_INCLUDE_UNMODIFIED = 1u << 5,

	/**
	 * Normally, a type change between files will be converted into a
	 *  DELETED record for the old and an ADDED record for the new; this
	 *  options enabled the generation of TYPECHANGE delta records.
	 */
	GIT_DIFF_INCLUDE_TYPECHANGE = 1u << 6,

	/**
	 * Even with GIT_DIFF_INCLUDE_TYPECHANGE, blob->tree changes still
	 *  generally show as a DELETED blob.  This flag tries to correctly
	 *  label blob->tree transitions as TYPECHANGE records with new_file's
	 *  mode set to tree.  Note: the tree SHA will not be available.
	 */
	GIT_DIFF_INCLUDE_TYPECHANGE_TREES = 1u << 7,

	/**
	 * Ignore file mode changes
	 */
	GIT_DIFF_IGNORE_FILEMODE = 1u << 8,

	/**
	 * Treat all submodules as unmodified
	 */
	GIT_DIFF_IGNORE_SUBMODULES = 1u << 9,

	/**
	 * Use case insensitive filename comparisons
	 */
	GIT_DIFF_IGNORE_CASE = 1u << 10,

	/**
	 * May be combined with `GIT_DIFF_IGNORE_CASE` to specify that a file
	 *  that has changed case will be returned as an add/delete pair.
	 */
	GIT_DIFF_INCLUDE_CASECHANGE = 1u << 11,

	/**
	 * If the pathspec is set in the diff options, this flags indicates
	 *  that the paths will be treated as literal paths instead of
	 *  fnmatch patterns.  Each path in the list must either be a full
	 *  path to a file or a directory.  (A trailing slash indicates that
	 *  the path will _only_ match a directory).  If a directory is
	 *  specified, all children will be included.
	 */
	GIT_DIFF_DISABLE_PATHSPEC_MATCH = 1u << 12,

	/**
	 * Disable updating of the `binary` flag in delta records.  This is
	 *  useful when iterating over a diff if you don't need hunk and data
	 *  callbacks and want to avoid having to load file completely.
	 */
	GIT_DIFF_SKIP_BINARY_CHECK = 1u << 13,

	/**
	 * When diff finds an untracked directory, to match the behavior of
	 *  core Git, it scans the contents for IGNORED and UNTRACKED files.
	 *  If *all* contents are IGNORED, then the directory is IGNORED; if
	 *  any contents are not IGNORED, then the directory is UNTRACKED.
	 *  This is extra work that may not matter in many cases.  This flag
	 *  turns off that scan and immediately labels an untracked directory
	 *  as UNTRACKED (changing the behavior to not match core Git).
	 */
	GIT_DIFF_ENABLE_FAST_UNTRACKED_DIRS = 1u << 14,

	/**
	 * When diff finds a file in the working directory with stat
	 * information different from the index, but the OID ends up being the
	 * same, write the correct stat information into the index.  Note:
	 * without this flag, diff will always leave the index untouched.
	 */
	GIT_DIFF_UPDATE_INDEX = 1u << 15,

	/**
	 * Include unreadable files in the diff
	 */
	GIT_DIFF_INCLUDE_UNREADABLE = 1u << 16,

	/**
	 * Include unreadable files in the diff
	 */
	GIT_DIFF_INCLUDE_UNREADABLE_AS_UNTRACKED = 1u << 17,

	/*
	 * Options controlling how output will be generated
	 */

	/**
	 * Use a heuristic that takes indentation and whitespace into account
	 * which generally can produce better diffs when dealing with ambiguous
	 * diff hunks.
	 */
	GIT_DIFF_INDENT_HEURISTIC = 1u << 18,

	/**
	 * Treat all files as text, disabling binary attributes & detection
	 */
	GIT_DIFF_FORCE_TEXT = 1u << 20,

	/**
	 * Treat all files as binary, disabling text diffs
	 */
	GIT_DIFF_FORCE_BINARY = 1u << 21,

	/**
	 * Ignore all whitespace
	 */
	GIT_DIFF_IGNORE_WHITESPACE = 1u << 22,

	/**
	 * Ignore changes in amount of whitespace
	 */
	GIT_DIFF_IGNORE_WHITESPACE_CHANGE = 1u << 23,

	/**
	 * Ignore whitespace at end of line
	 */
	GIT_DIFF_IGNORE_WHITESPACE_EOL = 1u << 24,

	/**
	 * When generating patch text, include the content of untracked
	 *  files.  This automatically turns on GIT_DIFF_INCLUDE_UNTRACKED but
	 *  it does not turn on GIT_DIFF_RECURSE_UNTRACKED_DIRS.  Add that
	 *  flag if you want the content of every single UNTRACKED file.
	 */
	GIT_DIFF_SHOW_UNTRACKED_CONTENT = 1u << 25,

	/**
	 * When generating output, include the names of unmodified files if
	 *  they are included in the git_diff.  Normally these are skipped in
	 *  the formats that list files (e.g. name-only, name-status, raw).
	 *  Even with this, these will not be included in patch format.
	 */
	GIT_DIFF_SHOW_UNMODIFIED = 1u << 26,

	/**
	 * Use the "patience diff" algorithm
	 */
	GIT_DIFF_PATIENCE = 1u << 28,

	/**
	 * Take extra time to find minimal diff
	 */
	GIT_DIFF_MINIMAL = 1u << 29,

	/**
	 * Include the necessary deflate / delta information so that `git-apply`
	 *  can apply given diff information to binary files.
	 */
	GIT_DIFF_SHOW_BINARY = 1u << 30,
}

/**
 * The diff object that contains all individual file deltas.
 *
 * A `diff` represents the cumulative list of differences between two
 * snapshots of a repository (possibly filtered by a set of file name
 * patterns).
 *
 * Calculating diffs is generally done in two phases: building a list of
 * diffs then traversing it. This makes is easier to share logic across
 * the various types of diffs (tree vs tree, workdir vs index, etc.), and
 * also allows you to insert optional diff post-processing phases,
 * such as rename detection, in between the steps. When you are done with
 * a diff object, it must be freed.
 *
 * This is an opaque structure which will be allocated by one of the diff
 * generator functions below (such as `git_diff_tree_to_tree`). You are
 * responsible for releasing the object memory when done, using the
 * `git_diff_free()` function.
 */
struct git_diff;

/**
 * Flags for the delta object and the file objects on each side.
 *
 * These flags are used for both the `flags` value of the `git_diff_delta`
 * and the flags for the `git_diff_file` objects representing the old and
 * new sides of the delta.  Values outside of this public range should be
 * considered reserved for internal or future use.
 */
enum git_diff_flag_t
{
	/**
	 * file(s) treated as binary data
	 */
	GIT_DIFF_FLAG_BINARY = 1u << 0,

	/**
	 * file(s) treated as text data
	 */
	GIT_DIFF_FLAG_NOT_BINARY = 1u << 1,

	/**
	 * `id` value is known correct
	 */
	GIT_DIFF_FLAG_VALID_ID = 1u << 2,

	/**
	 * file exists at this side of the delta
	 */
	GIT_DIFF_FLAG_EXISTS = 1u << 3,
}

/**
 * What type of change is described by a git_diff_delta?
 *
 * `GIT_DELTA_RENAMED` and `GIT_DELTA_COPIED` will only show up if you run
 * `git_diff_find_similar()` on the diff object.
 *
 * `GIT_DELTA_TYPECHANGE` only shows up given `GIT_DIFF_INCLUDE_TYPECHANGE`
 * in the option flags (otherwise type changes will be split into ADDED /
 * DELETED pairs).
 */
enum git_delta_t
{
	/**
	 * no changes
	 */
	GIT_DELTA_UNMODIFIED = 0,

	/**
	 * entry does not exist in old version
	 */
	GIT_DELTA_ADDED = 1,

	/**
	 * entry does not exist in new version
	 */
	GIT_DELTA_DELETED = 2,

	/**
	 * entry content changed between old and new
	 */
	GIT_DELTA_MODIFIED = 3,

	/**
	 * entry was renamed between old and new
	 */
	GIT_DELTA_RENAMED = 4,

	/**
	 * entry was copied from another old entry
	 */
	GIT_DELTA_COPIED = 5,

	/**
	 * entry is ignored item in workdir
	 */
	GIT_DELTA_IGNORED = 6,

	/**
	 * entry is untracked item in workdir
	 */
	GIT_DELTA_UNTRACKED = 7,

	/**
	 * type of entry changed between old and new
	 */
	GIT_DELTA_TYPECHANGE = 8,

	/**
	 * entry is unreadable
	 */
	GIT_DELTA_UNREADABLE = 9,

	/**
	 * entry in the index is conflicted
	 */
	GIT_DELTA_CONFLICTED = 10,
}

/**
 * Description of one side of a delta.
 *
 * Although this is called a "file", it could represent a file, a symbolic
 * link, a submodule commit id, or even a tree (although that only if you
 * are tracking type changes or ignored/untracked directories).
 *
 * The `id` is the `git_oid` of the item.  If the entry represents an
 * absent side of a diff (e.g. the `old_file` of a `git_delta_t.GIT_DELTA_ADDED` delta),
 * then the oid will be zeroes.
 *
 * `path` is the NUL-terminated path to the entry relative to the working
 * directory of the repository.
 *
 * `size` is the size of the entry in bytes.
 *
 * `flags` is a combination of the `git_diff_flag_t` types
 *
 * `mode` is, roughly, the stat() `st_mode` value for the item.  This will
 * be restricted to one of the `libgit2_d.types.git_filemode_t` values.
 *
 * The `id_abbrev` represents the known length of the `id` field, when
 * converted to a hex string.  It is generally `GIT_OID_HEXSZ`, unless this
 * delta was created from reading a patch file, in which case it may be
 * abbreviated to something reasonable, like 7 characters.
 */
struct git_diff_file
{
	libgit2_d.oid.git_oid id;
	const (char)* path;
	libgit2_d.types.git_object_size_t size;
	uint flags;
	ushort mode;
	ushort id_abbrev;
}

/**
 * Description of changes to one entry.
 *
 * A `delta` is a file pair with an old and new revision.  The old version
 * may be absent if the file was just created and the new version may be
 * absent if the file was deleted.  A diff is mostly just a list of deltas.
 *
 * When iterating over a diff, this will be passed to most callbacks and
 * you can use the contents to understand exactly what has changed.
 *
 * The `old_file` represents the "from" side of the diff and the `new_file`
 * represents to "to" side of the diff.  What those means depend on the
 * function that was used to generate the diff and will be documented below.
 * You can also use the `git_diff_option_t.GIT_DIFF_REVERSE` flag to flip it around.
 *
 * Although the two sides of the delta are named "old_file" and "new_file",
 * they actually may correspond to entries that represent a file, a symbolic
 * link, a submodule commit id, or even a tree (if you are tracking type
 * changes or ignored/untracked directories).
 *
 * Under some circumstances, in the name of efficiency, not all fields will
 * be filled in, but we generally try to fill in as much as possible.  One
 * example is that the "flags" field may not have either the `BINARY` or the
 * `NOT_BINARY` flag set to avoid examining file contents if you do not pass
 * in hunk and/or line callbacks to the diff foreach iteration function.  It
 * will just use the git attributes for those files.
 *
 * The similarity score is zero unless you call `git_diff_find_similar()`
 * which does a similarity analysis of files in the diff.  Use that
 * function to do rename and copy detection, and to split heavily modified
 * files in add/delete pairs.  After that call, deltas with a status of
 * GIT_DELTA_RENAMED or GIT_DELTA_COPIED will have a similarity score
 * between 0 and 100 indicating how similar the old and new sides are.
 *
 * If you ask `git_diff_find_similar` to find heavily modified files to
 * break, but to not *actually* break the records, then GIT_DELTA_MODIFIED
 * records may have a non-zero similarity score if the self-similarity is
 * below the split threshold.  To display this value like core Git, invert
 * the score (a la `printf("M%03d", 100 - delta->similarity)`).
 */
struct git_diff_delta
{
	.git_delta_t status;

	/**
	 * git_diff_flag_t values
	 */
	uint flags;

	/**
	 * for RENAMED and COPIED, value 0-100
	 */
	ushort similarity;

	/**
	 * number of files in this delta
	 */
	ushort nfiles;

	.git_diff_file old_file;
	.git_diff_file new_file;
}

/**
 * Diff notification callback function.
 *
 * The callback will be called for each file, just before the `git_diff_delta`
 * gets inserted into the diff.
 *
 * When the callback:
 * - returns < 0, the diff process will be aborted.
 * - returns > 0, the delta will not be inserted into the diff, but the
 *		diff process continues.
 * - returns 0, the delta is inserted into the diff, and the diff process
 *		continues.
 */
alias git_diff_notify_cb = int function(const (.git_diff)* diff_so_far, const (.git_diff_delta)* delta_to_add, const (char)* matched_pathspec, void* payload);

/**
 * Diff progress callback.
 *
 * Called before each file comparison.
 *
 * Params:
 *      diff_so_far = The diff being generated.
 *      old_path = The path to the old file or null.
 *      new_path = The path to the new file or null.
 *
 * Returns: Non-zero to abort the diff.
 */
alias git_diff_progress_cb = int function(const (.git_diff)* diff_so_far, const (char)* old_path, const (char)* new_path, void* payload);

/**
 * Structure describing options about how the diff should be executed.
 *
 * Setting all values of the structure to zero will yield the default
 * values.  Similarly, passing null for the options structure will
 * give the defaults.  The default values are marked below.
 */
struct git_diff_options
{
	/**
	 * version for the struct
	 */
	uint version_;

	/**
	 * A combination of `git_diff_option_t` values above.
	 * Defaults to git_diff_option_t.GIT_DIFF_NORMAL
	 */
	uint flags;

	/* options controlling which files are in the diff */

	/**
	 * Overrides the submodule ignore setting for all submodules in the diff.
	 */
	libgit2_d.types.git_submodule_ignore_t ignore_submodules;

	/**
	 * An array of paths / fnmatch patterns to constrain diff.
	 * All paths are included by default.
	 */
	libgit2_d.strarray.git_strarray pathspec;

	/**
	 * An optional callback function, notifying the consumer of changes to
	 * the diff as new deltas are added.
	 */
	.git_diff_notify_cb notify_cb;

	/**
	 * An optional callback function, notifying the consumer of which files
	 * are being examined as the diff is generated.
	 */
	.git_diff_progress_cb progress_cb;

	/**
	 * The payload to pass to the callback functions.
	 */
	void* payload;

	/* options controlling how to diff text is generated */

	/**
	 * The number of unchanged lines that define the boundary of a hunk
	 * (and to display before and after). Defaults to 3.
	 */
	uint context_lines;

	/**
	 * The maximum number of unchanged lines between hunk boundaries before
	 * the hunks will be merged into one. Defaults to 0.
	 */
	uint interhunk_lines;

	/**
	 * The abbreviation length to use when formatting object ids.
	 * Defaults to the value of 'core.abbrev' from the config, or 7 if unset.
	 */
	ushort id_abbrev;

	/**
	 * A size (in bytes) above which a blob will be marked as binary
	 * automatically; pass a negative value to disable.
	 * Defaults to 512MB.
	 */
	libgit2_d.types.git_off_t max_size;

	/**
	 * The virtual "directory" prefix for old file names in hunk headers.
	 * Default is "a".
	 */
	const (char)* old_prefix;

	/**
	 * The virtual "directory" prefix for new file names in hunk headers.
	 * Defaults to "b".
	 */
	const (char)* new_prefix;
}

/**
 * The current version of the diff options structure
 */
enum GIT_DIFF_OPTIONS_VERSION = 1;

/*
 * Stack initializer for diff options.  Alternatively use
 * `git_diff_options_init` programmatic initialization.
 */

pragma(inline, true)
pure nothrow @safe @nogc
.git_diff_options GIT_DIFF_OPTIONS_INIT()

	do
	{
		libgit2_d.strarray.git_strarray PATHSPEC_OPTION =
		{
			strings: null,
			count: 0,
		};

		.git_diff_options OUTPUT =
		{
			version_: .GIT_DIFF_OPTIONS_VERSION,
			flags: 0,
			ignore_submodules: libgit2_d.types.git_submodule_ignore_t.GIT_SUBMODULE_IGNORE_UNSPECIFIED,
			pathspec: PATHSPEC_OPTION,
			notify_cb: null,
			progress_cb: null,
			payload: null,
			context_lines: 3,
		};

		return OUTPUT;
	}

/**
 * Initialize git_diff_options structure
 *
 * Initializes a `git_diff_options` with default values. Equivalent to creating
 * an instance with GIT_DIFF_OPTIONS_INIT.
 *
 * Params:
 *      opts = The `git_diff_options` struct to initialize.
 *      version = The struct version; pass `GIT_DIFF_OPTIONS_VERSION`.
 *
 * Returns: Zero on success; -1 on failure.
 */
//GIT_EXTERN
int git_diff_options_init(.git_diff_options* opts, uint version_);

/**
 * When iterating over a diff, callback that will be made per file.
 *
 * Params:
 *      delta = A pointer to the delta data for the file
 *      progress = Goes from 0 to 1 over the diff
 *      payload = User-specified pointer from foreach function
 */
alias git_diff_file_cb = int function(const (.git_diff_delta)* delta, float progress, void* payload);

enum GIT_DIFF_HUNK_HEADER_SIZE = 128;

/**
 * Structure describing the binary contents of a diff.
 *
 * A `binary` file / delta is a file (or pair) for which no text diffs
 * should be generated. A diff can contain delta entries that are
 * binary, but no diff content will be output for those files. There is
 * a base heuristic for binary detection and you can further tune the
 * behavior with git attributes or diff flags and option settings.
 */
enum git_diff_binary_t
{
	/**
	 * Whether there is data in this binary structure or not.
	 *
	 * If this is `1`, then this was produced and included binary content.
	 * If this is `0` then this was generated knowing only that a binary
	 * file changed but without providing the data, probably from a patch
	 * that said `Binary files a/file.txt and b/file.txt differ`.
	 */
	GIT_DIFF_BINARY_NONE,

	/**
	 * The binary data is the literal contents of the file.
	 */
	GIT_DIFF_BINARY_LITERAL,

	/**
	 * The binary data is the delta from one side to the other.
	 */
	GIT_DIFF_BINARY_DELTA,
}

/**
 * The contents of one of the files in a binary diff.
 */
struct git_diff_binary_file
{
	/**
	 * The type of binary data for this file.
	 */
	.git_diff_binary_t type;

	/**
	 * The binary data, deflated.
	 */
	const (char)* data;

	/**
	 * The length of the binary data.
	 */
	size_t datalen;

	/**
	 * The length of the binary data after inflation.
	 */
	size_t inflatedlen;
}

/**
 * Structure describing the binary contents of a diff.
 */
struct git_diff_binary
{
	/**
	 * Whether there is data in this binary structure or not.  If this
	 * is `1`, then this was produced and included binary content.  If
	 * this is `0` then this was generated knowing only that a binary
	 * file changed but without providing the data, probably from a patch
	 * that said `Binary files a/file.txt and b/file.txt differ`.
	 */
	uint contains_data;

	/**
	 * The contents of the old file.
	 */
	.git_diff_binary_file old_file;

	/**
	 * The contents of the new file.
	 */
	.git_diff_binary_file new_file;
}

/**
 * When iterating over a diff, callback that will be made for
 * binary content within the diff.
 */
alias git_diff_binary_cb = int function(const (.git_diff_delta)* delta, const (.git_diff_binary)* binary, void* payload);

/**
 * Structure describing a hunk of a diff.
 *
 * A `hunk` is a span of modified lines in a delta along with some stable
 * surrounding context. You can configure the amount of context and other
 * properties of how hunks are generated. Each hunk also comes with a
 * header that described where it starts and ends in both the old and new
 * versions in the delta.
 */
struct git_diff_hunk
{
	/**
	 * Starting line number in old_file
	 */
	int old_start;

	/**
	 * Number of lines in old_file
	 */
	int old_lines;

	/**
	 * Starting line number in new_file
	 */
	int new_start;

	/**
	 * Number of lines in new_file
	 */
	int new_lines;

	/**
	 * Number of bytes in header text
	 */
	size_t header_len;

	/**
	 * Header text, NUL-byte terminated
	 */
	char[.GIT_DIFF_HUNK_HEADER_SIZE] header = '\0'; 
}

/**
 * When iterating over a diff, callback that will be made per hunk.
 */
alias git_diff_hunk_cb = int function(const (.git_diff_delta)* delta, const (.git_diff_hunk)* hunk, void* payload);

/**
 * Line origin constants.
 *
 * These values describe where a line came from and will be passed to
 * the git_diff_line_cb when iterating over a diff.  There are some
 * special origin constants at the end that are used for the text
 * output callbacks to demarcate lines that are actually part of
 * the file or hunk headers.
 */
enum git_diff_line_t
{
	/* These values will be sent to `git_diff_line_cb` along with the line */
	GIT_DIFF_LINE_CONTEXT = ' ',
	GIT_DIFF_LINE_ADDITION = '+',
	GIT_DIFF_LINE_DELETION = '-',

	/**
	 * Both files have no LF at end
	 */
	GIT_DIFF_LINE_CONTEXT_EOFNL = '=',

	/**
	 * Old has no LF at end, new does
	 */
	GIT_DIFF_LINE_ADD_EOFNL = '>',

	/**
	 * Old has LF at end, new does not
	 */
	GIT_DIFF_LINE_DEL_EOFNL = '<',

	/*
	 * The following values will only be sent to a `git_diff_line_cb` when
	 * the content of a diff is being formatted through `git_diff_print`.
	 */
	GIT_DIFF_LINE_FILE_HDR = 'F',
	GIT_DIFF_LINE_HUNK_HDR = 'H',

	/**
	 * For "Binary files x and y differ"
	 */
	GIT_DIFF_LINE_BINARY = 'B',
}

/**
 * Structure describing a line (or data span) of a diff.
 *
 * A `line` is a range of characters inside a hunk.  It could be a context
 * line (i.e. in both old and new versions), an added line (i.e. only in
 * the new version), or a removed line (i.e. only in the old version).
 * Unfortunately, we don't know anything about the encoding of data in the
 * file being diffed, so we cannot tell you much about the line content.
 * Line data will not be NUL-byte terminated, however, because it will be
 * just a span of bytes inside the larger file.
 */
struct git_diff_line
{
	/**
	 * A git_diff_line_t value
	 */
	char origin = '\0';

	/**
	 * Line number in old file or -1 for added line
	 */
	int old_lineno;

	/**
	 * Line number in new file or -1 for deleted line
	 */
	int new_lineno;

	/**
	 * Number of newline characters in content
	 */
	int num_lines;

	/**
	 * Number of bytes of data
	 */
	size_t content_len;

	/**
	 * Offset in the original file to the content
	 */
	libgit2_d.types.git_off_t content_offset;

	/**
	 * Pointer to diff text, not NUL-byte terminated
	 */
	const (char)* content;
}

/**
 * When iterating over a diff, callback that will be made per text diff
 * line. In this context, the provided range will be null.
 *
 * When printing a diff, callback that will be made to output each line
 * of text.  This uses some extra GIT_DIFF_LINE_... constants for output
 * of lines of file and hunk headers.
 */
alias git_diff_line_cb = int function(
    const (.git_diff_delta)* delta, /**< delta that contains this data */
    const (.git_diff_hunk)* hunk,   /**< hunk containing this data */
    const (.git_diff_line)* line,   /**< line data */
    void* payload);              /**< user reference data */

/**
 * Flags to control the behavior of diff rename/copy detection.
 */
enum git_diff_find_t
{
	/**
	 * Obey `diff.renames`. Overridden by any other GIT_DIFF_FIND_... flag.
	 */
	GIT_DIFF_FIND_BY_CONFIG = 0,

	/**
	 * Look for renames? (`--find-renames`)
	 */
	GIT_DIFF_FIND_RENAMES = 1u << 0,

	/**
	 * Consider old side of MODIFIED for renames? (`--break-rewrites=N`)
	 */
	GIT_DIFF_FIND_RENAMES_FROM_REWRITES = 1u << 1,

	/**
	 * Look for copies? (a la `--find-copies`).
	 */
	GIT_DIFF_FIND_COPIES = 1u << 2,

	/**
	 * Consider UNMODIFIED as copy sources? (`--find-copies-harder`).
	 *
	 * For this to work correctly, use git_diff_option_t.GIT_DIFF_INCLUDE_UNMODIFIED when
	 * the initial `git_diff` is being generated.
	 */
	GIT_DIFF_FIND_COPIES_FROM_UNMODIFIED = 1u << 3,

	/**
	 * Mark significant rewrites for split (`--break-rewrites=/M`)
	 */
	GIT_DIFF_FIND_REWRITES = 1u << 4,

	/**
	 * Actually split large rewrites into delete/add pairs
	 */
	GIT_DIFF_BREAK_REWRITES = 1u << 5,

	/**
	 * Mark rewrites for split and break into delete/add pairs
	 */
	GIT_DIFF_FIND_AND_BREAK_REWRITES = GIT_DIFF_FIND_REWRITES | GIT_DIFF_BREAK_REWRITES,

	/**
	 * Find renames/copies for UNTRACKED items in working directory.
	 *
	 * For this to work correctly, use git_diff_option_t.GIT_DIFF_INCLUDE_UNTRACKED when the
	 * initial `git_diff` is being generated (and obviously the diff must
	 * be against the working directory for this to make sense).
	 */
	GIT_DIFF_FIND_FOR_UNTRACKED = 1u << 6,

	/**
	 * Turn on all finding features.
	 */
	GIT_DIFF_FIND_ALL = 0x00FF,

	/**
	 * Measure similarity ignoring leading whitespace (default)
	 */
	GIT_DIFF_FIND_IGNORE_LEADING_WHITESPACE = 0,

	/**
	 * Measure similarity ignoring all whitespace
	 */
	GIT_DIFF_FIND_IGNORE_WHITESPACE = 1u << 12,

	/**
	 * Measure similarity including all data
	 */
	GIT_DIFF_FIND_DONT_IGNORE_WHITESPACE = 1u << 13,

	/**
	 * Measure similarity only by comparing SHAs (fast and cheap)
	 */
	GIT_DIFF_FIND_EXACT_MATCH_ONLY = 1u << 14,

	/**
	 * Do not break rewrites unless they contribute to a rename.
	 *
	 * Normally, GIT_DIFF_FIND_AND_BREAK_REWRITES will measure the self-
	 * similarity of modified files and split the ones that have changed a
	 * lot into a DELETE / ADD pair.  Then the sides of that pair will be
	 * considered candidates for rename and copy detection.
	 *
	 * If you add this flag in and the split pair is *not* used for an
	 * actual rename or copy, then the modified record will be restored to
	 * a regular MODIFIED record instead of being split.
	 */
	GIT_DIFF_BREAK_REWRITES_FOR_RENAMES_ONLY = 1u << 15,

	/**
	 * Remove any UNMODIFIED deltas after find_similar is done.
	 *
	 * Using GIT_DIFF_FIND_COPIES_FROM_UNMODIFIED to emulate the
	 * --find-copies-harder behavior requires building a diff with the
	 * GIT_DIFF_INCLUDE_UNMODIFIED flag.  If you do not want UNMODIFIED
	 * records in the final result, pass this flag to have them removed.
	 */
	GIT_DIFF_FIND_REMOVE_UNMODIFIED = 1u << 16,
}

/**
 * Pluggable similarity metric
 */
struct git_diff_similarity_metric
{
	int function(void** out_, const (.git_diff_file)* file, const (char)* fullpath, void* payload) file_signature;
	int function(void** out_, const (.git_diff_file)* file, const (char)* buf, size_t buflen, void* payload) buffer_signature;
	void function(void* sig, void* payload) free_signature;
	int function(int* score, void* siga, void* sigb, void* payload) similarity;
	void* payload;
}

/**
 * Control behavior of rename and copy detection
 *
 * These options mostly mimic parameters that can be passed to git-diff.
 */
struct git_diff_find_options
{
	uint version_;

	/**
	 * Combination of git_diff_find_t values (default git_diff_find_t.GIT_DIFF_FIND_BY_CONFIG).
	 * NOTE: if you don't explicitly set this, `diff.renames` could be set
	 * to false, resulting in `git_diff_find_similar` doing nothing.
	 */
	uint flags;

	/**
	 * Threshold above which similar files will be considered renames.
	 * This is equivalent to the -M option. Defaults to 50.
	 */
	ushort rename_threshold;

	/**
	 * Threshold below which similar files will be eligible to be a rename source.
	 * This is equivalent to the first part of the -B option. Defaults to 50.
	 */
	ushort rename_from_rewrite_threshold;

	/**
	 * Threshold above which similar files will be considered copies.
	 * This is equivalent to the -C option. Defaults to 50.
	 */
	ushort copy_threshold;

	/**
	 * Treshold below which similar files will be split into a delete/add pair.
	 * This is equivalent to the last part of the -B option. Defaults to 60.
	 */
	ushort break_rewrite_threshold;

	/**
	 * Maximum number of matches to consider for a particular file.
	 *
	 * This is a little different from the `-l` option from Git because we
	 * will still process up to this many matches before abandoning the search.
	 * Defaults to 200.
	 */
	size_t rename_limit;

	/**
	 * The `metric` option allows you to plug in a custom similarity metric.
	 *
	 * Set it to NULL to use the default internal metric.
	 *
	 * The default metric is based on sampling hashes of ranges of data in
	 * the file, which is a pretty good similarity approximation that should
	 * work fairly well for both text and binary data while still being
	 * pretty fast with a fixed memory overhead.
	 */
	.git_diff_similarity_metric* metric;
}

enum GIT_DIFF_FIND_OPTIONS_VERSION = 1;

pragma(inline, true)
pure nothrow @safe @nogc
.git_diff_find_options GIT_DIFF_FIND_OPTIONS_INIT()

	do
	{
		.git_diff_find_options OUTPUT =
		{
			version_: .GIT_DIFF_FIND_OPTIONS_VERSION,
		};

		return OUTPUT;
	}

/**
 * Initialize git_diff_find_options structure
 *
 * Initializes a `git_diff_find_options` with default values. Equivalent to creating
 * an instance with GIT_DIFF_FIND_OPTIONS_INIT.
 *
 * Params:
 *      opts = The `git_diff_find_options` struct to initialize.
 *      version = The struct version; pass `GIT_DIFF_FIND_OPTIONS_VERSION`.
 *
 * Returns: Zero on success; -1 on failure.
 */
//GIT_EXTERN
int git_diff_find_options_init(.git_diff_find_options* opts, uint version_);

/**
 * @name Diff Generator Functions
 *
 * These are the functions you would use to create (or destroy) a
 * git_diff from various objects in a repository.
 */
/**@{*/

/**
 * Deallocate a diff.
 *
 * Params:
 *      diff = The previously created diff; cannot be used after free.
 */
//GIT_EXTERN
void git_diff_free(.git_diff* diff);

/**
 * Create a diff with the difference between two tree objects.
 *
 * This is equivalent to `git diff <old-tree> <new-tree>`
 *
 * The first tree will be used for the "old_file" side of the delta and the
 * second tree will be used for the "new_file" side of the delta.  You can
 * pass null to indicate an empty tree, although it is an error to pass
 * null for both the `old_tree` and `new_tree`.
 *
 * Params:
 *      diff = Output pointer to a git_diff pointer to be allocated.
 *      repo = The repository containing the trees.
 *      old_tree = A git_tree object to diff from, or null for empty tree.
 *      new_tree = A git_tree object to diff to, or null for empty tree.
 *      opts = Structure with options to influence diff or null for defaults.
 */
//GIT_EXTERN
int git_diff_tree_to_tree(.git_diff** diff, libgit2_d.types.git_repository* repo, libgit2_d.types.git_tree* old_tree, libgit2_d.types.git_tree* new_tree, const (.git_diff_options)* opts);

/**
 * Create a diff between a tree and repository index.
 *
 * This is equivalent to `git diff --cached <treeish>` or if you pass
 * the HEAD tree, then like `git diff --cached`.
 *
 * The tree you pass will be used for the "old_file" side of the delta, and
 * the index will be used for the "new_file" side of the delta.
 *
 * If you pass null for the index, then the existing index of the `repo`
 * will be used.  In this case, the index will be refreshed from disk
 * (if it has changed) before the diff is generated.
 *
 * Params:
 *      diff = Output pointer to a git_diff pointer to be allocated.
 *      repo = The repository containing the tree and index.
 *      old_tree = A git_tree object to diff from, or null for empty tree.
 *      index = The index to diff with; repo index used if null.
 *      opts = Structure with options to influence diff or null for defaults.
 */
//GIT_EXTERN
int git_diff_tree_to_index(.git_diff** diff, libgit2_d.types.git_repository* repo, libgit2_d.types.git_tree* old_tree, libgit2_d.types.git_index* index, const (.git_diff_options)* opts);

/**
 * Create a diff between the repository index and the workdir directory.
 *
 * This matches the `git diff` command.  See the note below on
 * `git_diff_tree_to_workdir` for a discussion of the difference between
 * `git diff` and `git diff HEAD` and how to emulate a `git diff <treeish>`
 * using libgit2.
 *
 * The index will be used for the "old_file" side of the delta, and the
 * working directory will be used for the "new_file" side of the delta.
 *
 * If you pass null for the index, then the existing index of the `repo`
 * will be used.  In this case, the index will be refreshed from disk
 * (if it has changed) before the diff is generated.
 *
 * Params:
 *      diff = Output pointer to a git_diff pointer to be allocated.
 *      repo = The repository.
 *      index = The index to diff from; repo index used if null.
 *      opts = Structure with options to influence diff or null for defaults.
 */
//GIT_EXTERN
int git_diff_index_to_workdir(.git_diff** diff, libgit2_d.types.git_repository* repo, libgit2_d.types.git_index* index, const (.git_diff_options)* opts);

/**
 * Create a diff between a tree and the working directory.
 *
 * The tree you provide will be used for the "old_file" side of the delta,
 * and the working directory will be used for the "new_file" side.
 *
 * This is not the same as `git diff <treeish>` or `git diff-index
 * <treeish>`.  Those commands use information from the index, whereas this
 * function strictly returns the differences between the tree and the files
 * in the working directory, regardless of the state of the index.  Use
 * `git_diff_tree_to_workdir_with_index` to emulate those commands.
 *
 * To see difference between this and `git_diff_tree_to_workdir_with_index`,
 * consider the example of a staged file deletion where the file has then
 * been put back into the working dir and further modified.  The
 * tree-to-workdir diff for that file is 'modified', but `git diff` would
 * show status 'deleted' since there is a staged delete.
 *
 * Params:
 *      diff = A pointer to a git_diff pointer that will be allocated.
 *      repo = The repository containing the tree.
 *      old_tree = A git_tree object to diff from, or null for empty tree.
 *      opts = Structure with options to influence diff or null for defaults.
 */
//GIT_EXTERN
int git_diff_tree_to_workdir(.git_diff** diff, libgit2_d.types.git_repository* repo, libgit2_d.types.git_tree* old_tree, const (.git_diff_options)* opts);

/**
 * Create a diff between a tree and the working directory using index data
 * to account for staged deletes, tracked files, etc.
 *
 * This emulates `git diff <tree>` by diffing the tree to the index and
 * the index to the working directory and blending the results into a
 * single diff that includes staged deleted, etc.
 *
 * Params:
 *      diff = A pointer to a git_diff pointer that will be allocated.
 *      repo = The repository containing the tree.
 *      old_tree = A git_tree object to diff from, or null for empty tree.
 *      opts = Structure with options to influence diff or null for defaults.
 */
//GIT_EXTERN
int git_diff_tree_to_workdir_with_index(.git_diff** diff, libgit2_d.types.git_repository* repo, libgit2_d.types.git_tree* old_tree, const (.git_diff_options)* opts);

/**
 * Create a diff with the difference between two index objects.
 *
 * The first index will be used for the "old_file" side of the delta and the
 * second index will be used for the "new_file" side of the delta.
 *
 * Params:
 *      diff = Output pointer to a git_diff pointer to be allocated.
 *      repo = The repository containing the indexes.
 *      old_index = A git_index object to diff from.
 *      new_index = A git_index object to diff to.
 *      opts = Structure with options to influence diff or null for defaults.
 */
//GIT_EXTERN
int git_diff_index_to_index(.git_diff** diff, libgit2_d.types.git_repository* repo, libgit2_d.types.git_index* old_index, libgit2_d.types.git_index* new_index, const (.git_diff_options)* opts);

/**
 * Merge one diff into another.
 *
 * This merges items from the "from" list into the "onto" list.  The
 * resulting diff will have all items that appear in either list.
 * If an item appears in both lists, then it will be "merged" to appear
 * as if the old version was from the "onto" list and the new version
 * is from the "from" list (with the exception that if the item has a
 * pending DELETE in the middle, then it will show as deleted).
 *
 * Params:
 *      onto = Diff to merge into.
 *      from = Diff to merge.
 */
//GIT_EXTERN
int git_diff_merge(.git_diff* onto, const (.git_diff)* from);

/**
 * Transform a diff marking file renames, copies, etc.
 *
 * This modifies a diff in place, replacing old entries that look
 * like renames or copies with new entries reflecting those changes.
 * This also will, if requested, break modified files into add/remove
 * pairs if the amount of change is above a threshold.
 *
 * Params:
 *      diff = diff to run detection algorithms on
 *      options = Control how detection should be run, null for defaults
 *
 * Returns: 0 on success, -1 on failure
 */
//GIT_EXTERN
int git_diff_find_similar(.git_diff* diff, const (.git_diff_find_options)* options);

/**@}*/

/**
 * @name Diff Processor Functions
 *
 * These are the functions you apply to a diff to process it
 * or read it in some way.
 */
/**@{*/

/**
 * Query how many diff records are there in a diff.
 *
 * Params:
 *      diff = A git_diff generated by one of the above functions
 *
 * Returns: Count of number of deltas in the list
 */
//GIT_EXTERN
size_t git_diff_num_deltas(const (.git_diff)* diff);

/**
 * Query how many diff deltas are there in a diff filtered by type.
 *
 * This works just like `git_diff_entrycount()` with an extra parameter
 * that is a `git_delta_t` and returns just the count of how many deltas
 * match that particular type.
 *
 * Params:
 *      diff = A git_diff generated by one of the above functions
 *      type = A git_delta_t value to filter the count
 *
 * Returns: Count of number of deltas matching delta_t type
 */
//GIT_EXTERN
size_t git_diff_num_deltas_of_type(const (.git_diff)* diff, .git_delta_t type);

/**
 * Return the diff delta for an entry in the diff list.
 *
 * The `git_diff_delta` pointer points to internal data and you do not
 * have to release it when you are done with it.  It will go away when
 * the * `git_diff` (or any associated `git_patch`) goes away.
 *
 * Note that the flags on the delta related to whether it has binary
 * content or not may not be set if there are no attributes set for the
 * file and there has been no reason to load the file data at this point.
 * For now, if you need those flags to be up to date, your only option is
 * to either use `git_diff_foreach` or create a `git_patch`.
 *
 * Params:
 *      diff = Diff list object
 *      idx = Index into diff list
 *
 * Returns: Pointer to git_diff_delta (or null if `idx` out of range)
 */
//GIT_EXTERN
const (.git_diff_delta)* git_diff_get_delta(const (.git_diff)* diff, size_t idx);

/**
 * Check if deltas are sorted case sensitively or insensitively.
 *
 * Params:
 *      diff = diff to check
 *
 * Returns: 0 if case sensitive, 1 if case is ignored
 */
//GIT_EXTERN
int git_diff_is_sorted_icase(const (.git_diff)* diff);

/**
 * Loop over all deltas in a diff issuing callbacks.
 *
 * This will iterate through all of the files described in a diff.  You
 * should provide a file callback to learn about each file.
 *
 * The "hunk" and "line" callbacks are optional, and the text diff of the
 * files will only be calculated if they are not null.  Of course, these
 * callbacks will not be invoked for binary files on the diff or for
 * files whose only changed is a file mode change.
 *
 * Returning a non-zero value from any of the callbacks will terminate
 * the iteration and return the value to the user.
 *
 * Params:
 *      diff = A git_diff generated by one of the above functions.
 *      file_cb = Callback function to make per file in the diff.
 *      binary_cb = Optional callback to make for binary files.
 *      hunk_cb = Optional callback to make per hunk of text diff.  This callback is called to describe a range of lines in the diff.  It will not be issued for binary files.
 *      line_cb = Optional callback to make per line of diff text.  This same callback will be made for context lines, added, and removed lines, and even for a deleted trailing newline.
 *      payload = Reference pointer that will be passed to your callbacks.
 *
 * Returns: 0 on success, non-zero callback return value, or error code
 */
//GIT_EXTERN
int git_diff_foreach(.git_diff* diff, .git_diff_file_cb file_cb, .git_diff_binary_cb binary_cb, .git_diff_hunk_cb hunk_cb, .git_diff_line_cb line_cb, void* payload);

/**
 * Look up the single character abbreviation for a delta status code.
 *
 * When you run `git diff --name-status` it uses single letter codes in
 * the output such as 'A' for added, 'D' for deleted, 'M' for modified,
 * etc.  This function converts a git_delta_t value into these letters for
 * your own purposes.  git_delta_t.GIT_DELTA_UNTRACKED will return a space (i.e. ' ').
 *
 * Params:
 *      status = The git_delta_t value to look up
 *
 * Returns: The single character label for that code
 */
//GIT_EXTERN
char git_diff_status_char(.git_delta_t status);

/**
 * Possible output formats for diff data
 */
enum git_diff_format_t
{
	/**
	 * full git diff
	 */
	GIT_DIFF_FORMAT_PATCH = 1u,

	/**
	 * just the file headers of patch
	 */
	GIT_DIFF_FORMAT_PATCH_HEADER = 2u,

	/**
	 * like git diff --raw
	 */
	GIT_DIFF_FORMAT_RAW = 3u,

	/**
	 * like git diff --name-only
	 */
	GIT_DIFF_FORMAT_NAME_ONLY = 4u,

	/**
	 * like git diff --name-status
	 */
	GIT_DIFF_FORMAT_NAME_STATUS = 5u,

	/**
	 * git diff as used by git patch-id
	 */
	GIT_DIFF_FORMAT_PATCH_ID = 6u,
}

/**
 * Iterate over a diff generating formatted text output.
 *
 * Returning a non-zero value from the callbacks will terminate the
 * iteration and return the non-zero value to the caller.
 *
 * Params:
 *      diff = A git_diff generated by one of the above functions.
 *      format = A git_diff_format_t value to pick the text format.
 *      print_cb = Callback to make per line of diff text.
 *      payload = Reference pointer that will be passed to your callback.
 *
 * Returns: 0 on success, non-zero callback return value, or error code
 */
//GIT_EXTERN
int git_diff_print(.git_diff* diff, .git_diff_format_t format, .git_diff_line_cb print_cb, void* payload);

/**
 * Produce the complete formatted text output from a diff into a
 * buffer.
 *
 * Params:
 *      out_ = A pointer to a user-allocated git_buf that will contain the diff text
 *      diff = A git_diff generated by one of the above functions.
 *      format = A git_diff_format_t value to pick the text format.
 *
 * Returns: 0 on success or error code
 */
//GIT_EXTERN
int git_diff_to_buf(libgit2_d.buffer.git_buf* out_, .git_diff* diff, .git_diff_format_t format);

/**@}*/

/*
 * Misc
 */

/**
 * Directly run a diff on two blobs.
 *
 * Compared to a file, a blob lacks some contextual information. As such,
 * the `git_diff_file` given to the callback will have some fake data; i.e.
 * `mode` will be 0 and `path` will be null.
 *
 * null is allowed for either `old_blob` or `new_blob` and will be treated
 * as an empty blob, with the `oid` set to null in the `git_diff_file` data.
 * Passing null for both blobs is a noop; no callbacks will be made at all.
 *
 * We do run a binary content check on the blob content and if either blob
 * looks like binary data, the `git_diff_delta` binary attribute will be set
 * to 1 and no call to the hunk_cb nor line_cb will be made (unless you pass
 * `git_diff_option_t.GIT_DIFF_FORCE_TEXT` of course).
 *
 * Params:
 *      old_blob = Blob for old side of diff, or null for empty blob
 *      old_as_path = Treat old blob as if it had this filename; can be null
 *      new_blob = Blob for new side of diff, or null for empty blob
 *      new_as_path = Treat new blob as if it had this filename; can be null
 *      options = Options for diff, or null for default options
 *      file_cb = Callback for "file"; made once if there is a diff; can be null
 *      binary_cb = Callback for binary files; can be null
 *      hunk_cb = Callback for each hunk in diff; can be null
 *      line_cb = Callback for each line in diff; can be null
 *      payload = Payload passed to each callback function
 *
 * Returns: 0 on success, non-zero callback return value, or error code
 */
//GIT_EXTERN
int git_diff_blobs(const (libgit2_d.types.git_blob)* old_blob, const (char)* old_as_path, const (libgit2_d.types.git_blob)* new_blob, const (char)* new_as_path, const (.git_diff_options)* options, .git_diff_file_cb file_cb, .git_diff_binary_cb binary_cb, .git_diff_hunk_cb hunk_cb, .git_diff_line_cb line_cb, void* payload);

/**
 * Directly run a diff between a blob and a buffer.
 *
 * As with `git_diff_blobs`, comparing a blob and buffer lacks some context,
 * so the `git_diff_file` parameters to the callbacks will be faked a la the
 * rules for `git_diff_blobs()`.
 *
 * Passing null for `old_blob` will be treated as an empty blob (i.e. the
 * `file_cb` will be invoked with git_delta_t.GIT_DELTA_ADDED and the diff will be the
 * entire content of the buffer added).  Passing null to the buffer will do
 * the reverse, with GIT_DELTA_REMOVED and blob content removed.
 *
 * Params:
 *      old_blob = Blob for old side of diff, or null for empty blob
 *      old_as_path = Treat old blob as if it had this filename; can be null
 *      buffer = Raw data for new side of diff, or null for empty
 *      buffer_len = Length of raw data for new side of diff
 *      buffer_as_path = Treat buffer as if it had this filename; can be null
 *      options = Options for diff, or null for default options
 *      file_cb = Callback for "file"; made once if there is a diff; can be null
 *      binary_cb = Callback for binary files; can be null
 *      hunk_cb = Callback for each hunk in diff; can be null
 *      line_cb = Callback for each line in diff; can be null
 *      payload = Payload passed to each callback function
 *
 * Returns: 0 on success, non-zero callback return value, or error code
 */
//GIT_EXTERN
int git_diff_blob_to_buffer(const (libgit2_d.types.git_blob)* old_blob, const (char)* old_as_path, const (char)* buffer, size_t buffer_len, const (char)* buffer_as_path, const (.git_diff_options)* options, .git_diff_file_cb file_cb, .git_diff_binary_cb binary_cb, .git_diff_hunk_cb hunk_cb, .git_diff_line_cb line_cb, void* payload);

/**
 * Directly run a diff between two buffers.
 *
 * Even more than with `git_diff_blobs`, comparing two buffer lacks
 * context, so the `git_diff_file` parameters to the callbacks will be
 * faked a la the rules for `git_diff_blobs()`.
 *
 * Params:
 *      old_buffer = Raw data for old side of diff, or null for empty
 *      old_len = Length of the raw data for old side of the diff
 *      old_as_path = Treat old buffer as if it had this filename; can be null
 *      new_buffer = Raw data for new side of diff, or null for empty
 *      new_len = Length of raw data for new side of diff
 *      new_as_path = Treat buffer as if it had this filename; can be null
 *      options = Options for diff, or null for default options
 *      file_cb = Callback for "file"; made once if there is a diff; can be null
 *      binary_cb = Callback for binary files; can be null
 *      hunk_cb = Callback for each hunk in diff; can be null
 *      line_cb = Callback for each line in diff; can be null
 *      payload = Payload passed to each callback function
 *
 * Returns: 0 on success, non-zero callback return value, or error code
 */
//GIT_EXTERN
int git_diff_buffers(const (void)* old_buffer, size_t old_len, const (char)* old_as_path, const (void)* new_buffer, size_t new_len, const (char)* new_as_path, const (.git_diff_options)* options, .git_diff_file_cb file_cb, .git_diff_binary_cb binary_cb, .git_diff_hunk_cb hunk_cb, .git_diff_line_cb line_cb, void* payload);

/**
 * Read the contents of a git patch file into a `git_diff` object.
 *
 * The diff object produced is similar to the one that would be
 * produced if you actually produced it computationally by comparing
 * two trees, however there may be subtle differences.  For example,
 * a patch file likely contains abbreviated object IDs, so the
 * object IDs in a `git_diff_delta` produced by this function will
 * also be abbreviated.
 *
 * This function will only read patch files created by a git
 * implementation, it will not read unified diffs produced by
 * the `diff` program, nor any other types of patch files.
 *
 * Params:
 *      out_ = A pointer to a git_diff pointer that will be allocated.
 *      content = The contents of a patch file
 *      content_len = The length of the patch file contents
 *
 * Returns: 0 or an error code
 */
//GIT_EXTERN
int git_diff_from_buffer(.git_diff** out_, const (char)* content, size_t content_len);

/**
 * This is an opaque structure which is allocated by `git_diff_get_stats`.
 * You are responsible for releasing the object memory when done, using the
 * `git_diff_stats_free()` function.
 */
struct git_diff_stats;

/**
 * Formatting options for diff stats
 */
enum git_diff_stats_format_t
{
	/**
	 * No stats
	 */
	GIT_DIFF_STATS_NONE = 0,

	/**
	 * Full statistics, equivalent of `--stat`
	 */
	GIT_DIFF_STATS_FULL = 1u << 0,

	/**
	 * Short statistics, equivalent of `--shortstat`
	 */
	GIT_DIFF_STATS_SHORT = 1u << 1,

	/**
	 * Number statistics, equivalent of `--numstat`
	 */
	GIT_DIFF_STATS_NUMBER = 1u << 2,

	/**
	 * Extended header information such as creations, renames and mode changes,
	 * equivalent of `--summary`
	 */
	GIT_DIFF_STATS_INCLUDE_SUMMARY = 1u << 3,
}

/**
 * Accumulate diff statistics for all patches.
 *
 * Params:
 *      out_ = Structure containg the diff statistics.
 *      diff = A git_diff generated by one of the above functions.
 *
 * Returns: 0 on success; non-zero on error
 */
//GIT_EXTERN
int git_diff_get_stats(.git_diff_stats** out_, .git_diff* diff);

/**
 * Get the total number of files changed in a diff
 *
 * Params:
 *      stats = A `git_diff_stats` generated by one of the above functions.
 *
 * Returns: total number of files changed in the diff
 */
//GIT_EXTERN
size_t git_diff_stats_files_changed(const (.git_diff_stats)* stats);

/**
 * Get the total number of insertions in a diff
 *
 * Params:
 *      stats = A `git_diff_stats` generated by one of the above functions.
 *
 * Returns: total number of insertions in the diff
 */
//GIT_EXTERN
size_t git_diff_stats_insertions(const (.git_diff_stats)* stats);

/**
 * Get the total number of deletions in a diff
 *
 * Params:
 *      stats = A `git_diff_stats` generated by one of the above functions.
 *
 * Returns: total number of deletions in the diff
 */
//GIT_EXTERN
size_t git_diff_stats_deletions(const (.git_diff_stats)* stats);

/**
 * Print diff statistics to a `git_buf`.
 *
 * Params:
 *      out_ = buffer to store the formatted diff statistics in.
 *      stats = A `git_diff_stats` generated by one of the above functions.
 *      format = Formatting option.
 *      width = Target width for output (only affects git_diff_stats_format_t.GIT_DIFF_STATS_FULL)
 *
 * Returns: 0 on success; non-zero on error
 */
//GIT_EXTERN
int git_diff_stats_to_buf(libgit2_d.buffer.git_buf* out_, const (.git_diff_stats)* stats, .git_diff_stats_format_t format, size_t width);

/**
 * Deallocate a `git_diff_stats`.
 *
 * Params:
 *      stats = The previously created statistics object;
 * cannot be used after free.
 */
//GIT_EXTERN
void git_diff_stats_free(.git_diff_stats* stats);

/**
 * Formatting options for diff e-mail generation
 */
enum git_diff_format_email_flags_t
{
	/**
	 * Normal patch, the default
	 */
	GIT_DIFF_FORMAT_EMAIL_NONE = 0,

	/**
	 * Don't insert "[PATCH]" in the subject header
	 */
	GIT_DIFF_FORMAT_EMAIL_EXCLUDE_SUBJECT_PATCH_MARKER = 1 << 0,
}

/**
 * Options for controlling the formatting of the generated e-mail.
 */
struct git_diff_format_email_options
{
	uint version_;

	/**
	 * see `git_diff_format_email_flags_t` above
	 */
	uint flags;

	/**
	 * This patch number
	 */
	size_t patch_no;

	/**
	 * Total number of patches in this series
	 */
	size_t total_patches;

	/**
	 * id to use for the commit
	 */
	const (libgit2_d.oid.git_oid)* id;

	/**
	 * Summary of the change
	 */
	const (char)* summary;

	/**
	 * Commit message's body
	 */
	const (char)* body_;

	/**
	 * Author of the change
	 */
	const (libgit2_d.types.git_signature)* author;
}

enum GIT_DIFF_FORMAT_EMAIL_OPTIONS_VERSION = 1;

pragma(inline, true)
pure nothrow @safe @nogc
.git_diff_format_email_options GIT_DIFF_FORMAT_EMAIL_OPTIONS_INIT()

	do
	{
		.git_diff_format_email_options OUTPUT =
		{
			version_: .GIT_DIFF_FORMAT_EMAIL_OPTIONS_VERSION,
			flags: .git_diff_format_email_flags_t.GIT_DIFF_FORMAT_EMAIL_NONE,
			patch_no: 1,
			total_patches: 1,
			id: null,
			summary: null,
			body_: null,
			author: null,
		};

		return OUTPUT;
	}

/**
 * Create an e-mail ready patch from a diff.
 *
 * Params:
 *      out_ = buffer to store the e-mail patch in
 *      diff = containing the commit
 *      opts = structure with options to influence content and formatting.
 *
 * Returns: 0 or an error code
 */
//GIT_EXTERN
int git_diff_format_email(libgit2_d.buffer.git_buf* out_, .git_diff* diff, const (.git_diff_format_email_options)* opts);

/**
 * Create an e-mail ready patch for a commit.
 *
 * Does not support creating patches for merge commits (yet).
 *
 * Params:
 *      out_ = buffer to store the e-mail patch in
 *      repo = containing the commit
 *      commit = pointer to up commit
 *      patch_no = patch number of the commit
 *      total_patches = total number of patches in the patch set
 *      flags = determines the formatting of the e-mail
 *      diff_opts = structure with options to influence diff or null for defaults.
 *
 * Returns: 0 or an error code
 */
//GIT_EXTERN
int git_diff_commit_as_email(libgit2_d.buffer.git_buf* out_, libgit2_d.types.git_repository* repo, libgit2_d.types.git_commit* commit, size_t patch_no, size_t total_patches, uint flags, const (.git_diff_options)* diff_opts);

/**
 * Initialize git_diff_format_email_options structure
 *
 * Initializes a `git_diff_format_email_options` with default values. Equivalent
 * to creating an instance with GIT_DIFF_FORMAT_EMAIL_OPTIONS_INIT.
 *
 * Params:
 *      opts = The `git_blame_options` struct to initialize.
 *      version = The struct version; pass `GIT_DIFF_FORMAT_EMAIL_OPTIONS_VERSION`.
 *
 * Returns: Zero on success; -1 on failure.
 */
//GIT_EXTERN
int git_diff_format_email_options_init(.git_diff_format_email_options* opts, uint version_);

/**
 * Patch ID options structure
 *
 * Initialize with `GIT_PATCHID_OPTIONS_INIT`. Alternatively, you can
 * use `git_diff_patchid_options_init`.
 */
struct git_diff_patchid_options
{
	uint version_;
}

enum GIT_DIFF_PATCHID_OPTIONS_VERSION = 1;

pragma(inline, true)
pure nothrow @safe @nogc
.git_diff_patchid_options GIT_DIFF_PATCHID_OPTIONS_INIT()

	do
	{
		.git_diff_patchid_options OUTPUT =
		{
			version_: .GIT_DIFF_PATCHID_OPTIONS_VERSION,
		};

		return OUTPUT;
	}

/**
 * Initialize git_diff_patchid_options structure
 *
 * Initializes a `git_diff_patchid_options` with default values. Equivalent to
 * creating an instance with `GIT_DIFF_PATCHID_OPTIONS_INIT`.
 *
 * Params:
 *      opts = The `git_diff_patchid_options` struct to initialize.
 *      version = The struct version; pass `GIT_DIFF_PATCHID_OPTIONS_VERSION`.
 *
 * Returns: Zero on success; -1 on failure.
 */
//GIT_EXTERN
int git_diff_patchid_options_init(.git_diff_patchid_options* opts, uint version_);

/**
 * Calculate the patch ID for the given patch.
 *
 * Calculate a stable patch ID for the given patch by summing the
 * hash of the file diffs, ignoring whitespace and line numbers.
 * This can be used to derive whether two diffs are the same with
 * a high probability.
 *
 * Currently, this function only calculates stable patch IDs, as
 * defined in git-patch-id(1), and should in fact generate the
 * same IDs as the upstream git project does.
 *
 * Params:
 *      out_ = Pointer where the calculated patch ID should be stored
 *      diff = The diff to calculate the ID for
 *      opts = Options for how to calculate the patch ID. This is intended for future changes, as currently no options are available.
 *
 * Returns: 0 on success, an error code otherwise.
 */
//GIT_EXTERN
int git_diff_patchid(libgit2_d.oid.git_oid* out_, .git_diff* diff, .git_diff_patchid_options* opts);

/** @} */