stash: implement partial stashing by path

code has been moved from `git_stash_save` into `git_stash_save_with_opts` in order to handle cases where we want to partially stash using options or stash normally without partially stashed paths specified

Author: gitkraken-jacobw

include/git2/stash.h

@@ -45,6 +45,11 @@ typedef enum {
 	 * the working directory
 	 */
 	GIT_STASH_INCLUDE_IGNORED = (1 << 2),
+
+	/**
+	 * All changes in the index and working directory are left intact
+	 */
+	GIT_STASH_KEEP_ALL = (1 << 3),
 } git_stash_flags;
 
 /**
@@ -71,6 +76,65 @@ GIT_EXTERN(int) git_stash_save(
 	const char *message,
 	uint32_t flags);
 
+/**
+ * Stash save options structure
+ *
+ * Initialize with `GIT_STASH_SAVE_OPTIONS_INIT`. Alternatively, you can
+ * use `git_stash_save_options_init`.
+ *
+ */
+typedef struct git_stash_save_options {
+	unsigned int version;
+
+	/** The identity of the person performing the stashing. */
+	const git_signature *stasher;
+
+	/** Optional description along with the stashed state. */
+	const char *message;
+
+	/** Flags to control the stashing process. (see GIT_STASH_* above) */
+	uint32_t flags;
+
+	/** Optional paths that control which files are stashed. */
+	git_strarray paths;
+} git_stash_save_options;
+
+#define GIT_STASH_SAVE_OPTIONS_VERSION 1
+#define GIT_STASH_SAVE_OPTIONS_INIT { \
+	GIT_STASH_SAVE_OPTIONS_VERSION, \
+	NULL, \
+	NULL, \
+	GIT_STASH_DEFAULT }
+
+/**
+ * Initialize git_stash_save_options structure
+ *
+ * Initializes a `git_stash_save_options` with default values. Equivalent to
+ * creating an instance with `GIT_STASH_SAVE_OPTIONS_INIT`.
+ *
+ * @param opts The `git_stash_save_options` struct to initialize.
+ * @param version The struct version; pass `GIT_STASH_SAVE_OPTIONS_VERSION`.
+ * @return Zero on success; -1 on failure.
+ */
+GIT_EXTERN(int) git_stash_save_options_init(
+	git_stash_save_options *opts, unsigned int version);
+
+/**
+ * Save the local modifications to a new stash, with options.
+ * 
+ * @param out Object id of the commit containing the stashed state.
+ * This commit is also the target of the direct reference refs/stash.
+ *
+ * @param repo The owning repository.
+ *
+ * @param opts The stash options.
+ *
+ * @return 0 on success, GIT_ENOTFOUND where there's nothing to stash,
+ * or error code.
+ */
+GIT_EXTERN(int) git_stash_save_with_opts(
+	git_oid *out, git_repository *repo, git_stash_save_options *opts);
+
 /** Stash application flags. */
 typedef enum {
 	GIT_STASH_APPLY_DEFAULT = 0,

src/stash.c

@@ -194,6 +194,31 @@ static int stash_to_index(
 	return git_index_add(index, &entry);
 }
 
+static int stash_update_index_from_paths(
+	git_repository *repo,
+	git_index *index,
+	git_strarray *paths)
+{
+	unsigned int status_flags;
+	size_t i;
+	int error = 0;
+
+	for(i = 0; i < paths->count; i++) {
+		git_status_file(&status_flags, repo, paths->strings[i]);
+
+		if (status_flags & (GIT_STATUS_WT_DELETED | GIT_STATUS_INDEX_DELETED)) {
+			if ((error = git_index_remove(index, paths->strings[i], 0)) < 0)
+				return error;
+		}
+		else {
+			if ((error = stash_to_index(repo, index, paths->strings[i])) < 0)
+				return error;
+		}
+	}
+
+	return error;
+}
+
 static int stash_update_index_from_diff(
 	git_repository *repo,
 	git_index *index,
@@ -576,6 +601,50 @@ static int ensure_there_are_changes_to_stash(git_repository *repo, uint32_t flag
 	return error;
 }
 
+static int has_changes_cb(const char *path, unsigned int status, void *payload) {
+	GIT_UNUSED(path);
+	GIT_UNUSED(status);
+	GIT_UNUSED(payload);
+
+	if (status == GIT_STATUS_CURRENT)
+		return GIT_ENOTFOUND;
+
+	return 0;
+}
+
+static int ensure_there_are_changes_to_stash_paths(
+	git_repository *repo,
+	uint32_t flags,
+	git_strarray *paths)
+{
+	int error;
+	git_status_options opts = GIT_STATUS_OPTIONS_INIT;
+
+	opts.show  = GIT_STATUS_SHOW_INDEX_AND_WORKDIR;
+	opts.flags = GIT_STATUS_OPT_EXCLUDE_SUBMODULES
+		| GIT_STATUS_OPT_INCLUDE_UNMODIFIED
+		| GIT_STATUS_OPT_DISABLE_PATHSPEC_MATCH;
+
+	if (flags & GIT_STASH_INCLUDE_UNTRACKED)
+		opts.flags |= GIT_STATUS_OPT_INCLUDE_UNTRACKED |
+			GIT_STATUS_OPT_RECURSE_UNTRACKED_DIRS;
+
+	if (flags & GIT_STASH_INCLUDE_IGNORED)
+		opts.flags |= GIT_STATUS_OPT_INCLUDE_IGNORED |
+			GIT_STATUS_OPT_RECURSE_IGNORED_DIRS;
+	
+	git_strarray_copy(&opts.pathspec, paths);
+
+	error = git_status_foreach_ext(repo, &opts, has_changes_cb, NULL);
+
+	git_strarray_dispose(&opts.pathspec);
+
+	if (error == GIT_ENOTFOUND)
+		return create_error(GIT_ENOTFOUND, "one of the files does not have any changes to stash.");
+
+	return error;
+}
+
 static int reset_index_and_workdir(git_repository *repo, git_commit *commit, uint32_t flags)
 {
 	git_checkout_options opts = GIT_CHECKOUT_OPTIONS_INIT;
@@ -596,50 +665,87 @@ int git_stash_save(
 	const char *message,
 	uint32_t flags)
 {
-	git_index *index = NULL;
+	git_stash_save_options opts = GIT_STASH_SAVE_OPTIONS_INIT;
+	opts.stasher = stasher;
+	opts.message = message;
+	opts.flags = flags;
+	return git_stash_save_with_opts(out, repo, &opts);
+}
+
+int git_stash_save_with_opts(
+	git_oid *out, git_repository *repo, git_stash_save_options *opts)
+{
+	git_index *index = NULL, *paths_index = NULL;
 	git_commit *b_commit = NULL, *i_commit = NULL, *u_commit = NULL;
 	git_buf msg = GIT_BUF_INIT;
+	git_tree *tree = NULL;
+	git_reference *head = NULL;
 	int error;
 
 	GIT_ASSERT_ARG(out);
 	GIT_ASSERT_ARG(repo);
-	GIT_ASSERT_ARG(stasher);
 
 	if ((error = git_repository__ensure_not_bare(repo, "stash save")) < 0)
 		return error;
 
 	if ((error = retrieve_base_commit_and_message(&b_commit, &msg, repo)) < 0)
 		goto cleanup;
 
-	if ((error = ensure_there_are_changes_to_stash(repo, flags)) < 0)
+	if (opts->paths.count == 0 &&
+		  (error = ensure_there_are_changes_to_stash(repo, opts->flags)) < 0)
+		goto cleanup;
+	else if (opts->paths.count > 0 &&
+		  (error = ensure_there_are_changes_to_stash_paths(
+			  repo, opts->flags, &opts->paths)) < 0)
 		goto cleanup;
 
 	if ((error = git_repository_index(&index, repo)) < 0)
 		goto cleanup;
 
-	if ((error = commit_index(&i_commit, repo, index, stasher,
-				  git_buf_cstr(&msg), b_commit)) < 0)
+	if ((error = commit_index(&i_commit, repo, index, opts->stasher,
+			  git_buf_cstr(&msg), b_commit)) < 0)
 		goto cleanup;
 
-	if ((flags & (GIT_STASH_INCLUDE_UNTRACKED | GIT_STASH_INCLUDE_IGNORED)) &&
-	    (error = commit_untracked(&u_commit, repo, stasher,
-				      git_buf_cstr(&msg), i_commit, flags)) < 0)
+	if ((opts->flags & (GIT_STASH_INCLUDE_UNTRACKED | GIT_STASH_INCLUDE_IGNORED)) &&
+	    (error = commit_untracked(&u_commit, repo, opts->stasher,
+			  git_buf_cstr(&msg), i_commit, opts->flags)) < 0)
 		goto cleanup;
 
-	if ((error = prepare_worktree_commit_message(&msg, message)) < 0)
+	if ((error = prepare_worktree_commit_message(&msg, opts->message)) < 0)
 		goto cleanup;
 
-	if ((error = commit_worktree(out, repo, stasher, git_buf_cstr(&msg),
-				     i_commit, b_commit, u_commit)) < 0)
-		goto cleanup;
+	if (opts->paths.count == 0) {
+		if ((error = commit_worktree(out, repo, opts->stasher, git_buf_cstr(&msg),
+					     i_commit, b_commit, u_commit)) < 0)
+			goto cleanup;
+	} else {
+		if ((error = git_index_new(&paths_index)) < 0)
+			goto cleanup;
+	
+		if ((error = retrieve_head(&head, repo)) < 0)
+			goto cleanup;
+
+		if ((error = git_reference_peel((git_object**)&tree, head, GIT_OBJECT_TREE)) < 0)
+			goto cleanup;
+		
+		if ((error = git_index_read_tree(paths_index, tree)) < 0)
+			goto cleanup;
+		
+		if ((error = stash_update_index_from_paths(repo, paths_index, &opts->paths)) < 0)
+			goto cleanup;
+
+		if ((error = build_stash_commit_from_index(out, repo, opts->stasher, git_buf_cstr(&msg),
+				  i_commit, b_commit, u_commit, paths_index)) < 0)
+			goto cleanup;
+	}
 
 	git_buf_rtrim(&msg);
 
 	if ((error = update_reflog(out, repo, git_buf_cstr(&msg))) < 0)
 		goto cleanup;
 
-	if ((error = reset_index_and_workdir(repo, (flags & GIT_STASH_KEEP_INDEX) ? i_commit : b_commit,
-					     flags)) < 0)
+	if (!(opts->flags & GIT_STASH_KEEP_ALL) && (error = reset_index_and_workdir(repo,
+			  (opts->flags & GIT_STASH_KEEP_INDEX) ? i_commit : b_commit, opts->flags)) < 0)
 		goto cleanup;
 
 cleanup:
@@ -648,7 +754,10 @@ int git_stash_save(
 	git_commit_free(i_commit);
 	git_commit_free(b_commit);
 	git_commit_free(u_commit);
+	git_tree_free(tree);
+	git_reference_free(head);
 	git_index_free(index);
+	git_index_free(paths_index);
 
 	return error;
 }
@@ -833,6 +942,13 @@ int git_stash_apply_options_init(git_stash_apply_options *opts, unsigned int ver
 	return 0;
 }
 
+int git_stash_save_options_init(git_stash_save_options *opts, unsigned int version)
+{
+	GIT_INIT_STRUCTURE_FROM_TEMPLATE(
+		opts, version, git_stash_save_options, GIT_STASH_SAVE_OPTIONS_INIT);
+	return 0;
+}
+
 #ifndef GIT_DEPRECATE_HARD
 int git_stash_apply_init_options(git_stash_apply_options *opts, unsigned int version)
 {