Merge pull request #3018 from ethomson/stash_apply

Stash apply

6 files changed, 497 insertions, 43 deletions

diff --git a/src/checkout.c b/src/checkout.c
index a647ce0b9..6a1d28136 100644
--- a/src/checkout.c
+++ b/src/checkout.c
@@ -2397,7 +2397,7 @@ static int checkout_data_init(
 			 &data->can_symlink, repo, GIT_CVAR_SYMLINKS)) < 0)
 		goto cleanup;
 
-	if (!data->opts.baseline) {
+	if (!data->opts.baseline && !data->opts.baseline_index) {
 		data->opts_free_baseline = true;
 
 		error = checkout_lookup_head_tree(&data->opts.baseline, repo);
@@ -2501,12 +2501,21 @@ int git_checkout_iterator(
 		(error = git_iterator_for_workdir_ext(
 			&workdir, data.repo, data.opts.target_directory, index, NULL,
 			iterflags | GIT_ITERATOR_DONT_AUTOEXPAND,
-			data.pfx, data.pfx)) < 0 ||
-		(error = git_iterator_for_tree(
-			&baseline, data.opts.baseline,
-			iterflags, data.pfx, data.pfx)) < 0)
+			data.pfx, data.pfx)) < 0)
 		goto cleanup;
 
+	if (data.opts.baseline_index) {
+		if ((error = git_iterator_for_index(
+				&baseline, data.opts.baseline_index,
+				iterflags, data.pfx, data.pfx)) < 0)
+			goto cleanup;
+	} else {
+		if ((error = git_iterator_for_tree(
+				&baseline, data.opts.baseline,
+				iterflags, data.pfx, data.pfx)) < 0)
+			goto cleanup;
+	}
+
 	/* Should not have case insensitivity mismatch */
 	assert(git_iterator_ignore_case(workdir) == git_iterator_ignore_case(baseline));
 
diff --git a/src/index.c b/src/index.c
index 0d2a03e72..7c0c31052 100644
--- a/src/index.c
+++ b/src/index.c
@@ -2451,6 +2451,104 @@ int git_index_read_tree(git_index *index, const git_tree *tree)
 	return error;
 }
 
+int git_index_read_index(
+	git_index *index,
+	const git_index *new_index)
+{
+	git_vector new_entries = GIT_VECTOR_INIT,
+		remove_entries = GIT_VECTOR_INIT;
+	git_iterator *index_iterator = NULL;
+	git_iterator *new_iterator = NULL;
+	const git_index_entry *old_entry, *new_entry;
+	git_index_entry *entry;
+	size_t i;
+	int error;
+
+	if ((error = git_vector_init(&new_entries, new_index->entries.length, index->entries._cmp)) < 0 ||
+		(error = git_vector_init(&remove_entries, index->entries.length, NULL)) < 0)
+		goto done;
+
+	if ((error = git_iterator_for_index(&index_iterator,
+			index, GIT_ITERATOR_DONT_IGNORE_CASE, NULL, NULL)) < 0 ||
+		(error = git_iterator_for_index(&new_iterator,
+			(git_index *)new_index, GIT_ITERATOR_DONT_IGNORE_CASE, NULL, NULL)) < 0)
+		goto done;
+
+	if (((error = git_iterator_current(&old_entry, index_iterator)) < 0 && 
+			error != GIT_ITEROVER) ||
+		((error = git_iterator_current(&new_entry, new_iterator)) < 0 && 
+			error != GIT_ITEROVER))
+		goto done;
+
+	while (true) {
+		int diff;
+
+		if (old_entry && new_entry)
+			diff = git_index_entry_cmp(old_entry, new_entry);
+		else if (!old_entry && new_entry)
+			diff = 1;
+		else if (old_entry && !new_entry)
+			diff = -1;
+		else
+			break;
+
+		if (diff < 0) {
+			git_vector_insert(&remove_entries, (git_index_entry *)old_entry);
+		} else if (diff > 0) {
+			if ((error = index_entry_dup(&entry, git_index_owner(index), new_entry)) < 0)
+				goto done;
+
+			git_vector_insert(&new_entries, entry);
+		} else {
+			/* Path and stage are equal, if the OID is equal, keep it to
+			 * keep the stat cache data.
+			 */
+			if (git_oid_equal(&old_entry->id, &new_entry->id)) {
+				git_vector_insert(&new_entries, (git_index_entry *)old_entry);
+			} else {
+				if ((error = index_entry_dup(&entry, git_index_owner(index), new_entry)) < 0)
+					goto done;
+
+				git_vector_insert(&new_entries, entry);
+				git_vector_insert(&remove_entries, (git_index_entry *)old_entry);
+			}
+		}
+
+		if (diff <= 0) {
+			if ((error = git_iterator_advance(&old_entry, index_iterator)) < 0 &&
+				error != GIT_ITEROVER)
+				goto done;
+		}
+
+		if (diff >= 0) {
+			if ((error = git_iterator_advance(&new_entry, new_iterator)) < 0 &&
+				error != GIT_ITEROVER)
+				goto done;
+		}
+	}
+
+	git_index_name_clear(index);
+	git_index_reuc_clear(index);
+
+	git_vector_swap(&new_entries, &index->entries);
+
+	git_vector_foreach(&remove_entries, i, entry) {
+		if (index->tree)
+			git_tree_cache_invalidate_path(index->tree, entry->path);
+
+		index_entry_free(entry);
+	}
+
+	error = 0;
+
+done:
+	git_vector_free(&new_entries);
+	git_vector_free(&remove_entries);
+	git_iterator_free(index_iterator);
+	git_iterator_free(new_iterator);
+	return error;
+}
+
 git_repository *git_index_owner(const git_index *index)
 {
 	return INDEX_OWNER(index);
diff --git a/src/index.h b/src/index.h
index 6d2904fdc..0f6f4e86e 100644
--- a/src/index.h
+++ b/src/index.h
@@ -93,6 +93,8 @@ extern int git_index_snapshot_find(
 	size_t *at_pos, git_vector *snap, git_vector_cmp entry_srch,
 	const char *path, size_t path_len, int stage);
 
+/* Replace an index with a new index */
+int git_index_read_index(git_index *index, const git_index *new_index);
 
 typedef struct {
 	git_index *index;
diff --git a/src/merge.c b/src/merge.c
index bd676aacf..5e7727429 100644
--- a/src/merge.c
+++ b/src/merge.c
@@ -1451,11 +1451,11 @@ static int merge_diff_list_insert_unmodified(
 
 int git_merge_diff_list__find_differences(
 	git_merge_diff_list *diff_list,
-	const git_tree *ancestor_tree,
-	const git_tree *our_tree,
-	const git_tree *their_tree)
+	git_iterator *ancestor_iter,
+	git_iterator *our_iter,
+	git_iterator *their_iter)
 {
-	git_iterator *iterators[3] = {0};
+	git_iterator *iterators[3] = { ancestor_iter, our_iter, their_iter };
 	const git_index_entry *items[3] = {0}, *best_cur_item, *cur_items[3];
 	git_vector_cmp entry_compare = git_index_entry_cmp;
 	struct merge_diff_df_data df_data = {0};
@@ -1463,12 +1463,7 @@ int git_merge_diff_list__find_differences(
 	size_t i, j;
 	int error = 0;
 
-	assert(diff_list && (our_tree || their_tree));
-
-	if ((error = git_iterator_for_tree(&iterators[TREE_IDX_ANCESTOR], (git_tree *)ancestor_tree, GIT_ITERATOR_DONT_IGNORE_CASE, NULL, NULL)) < 0 ||
-		(error = git_iterator_for_tree(&iterators[TREE_IDX_OURS], (git_tree *)our_tree, GIT_ITERATOR_DONT_IGNORE_CASE, NULL, NULL)) < 0 ||
-		(error = git_iterator_for_tree(&iterators[TREE_IDX_THEIRS], (git_tree *)their_tree, GIT_ITERATOR_DONT_IGNORE_CASE, NULL, NULL)) < 0)
-		goto done;
+	assert(diff_list && (our_iter || their_iter));
 
 	/* Set up the iterators */
 	for (i = 0; i < 3; i++) {
@@ -1544,9 +1539,6 @@ int git_merge_diff_list__find_differences(
 	}
 
 done:
-	for (i = 0; i < 3; i++)
-		git_iterator_free(iterators[i]);
-
 	if (error == GIT_ITEROVER)
 		error = 0;
 
@@ -1757,14 +1749,28 @@ on_error:
 	return error;
 }
 
-int git_merge_trees(
+static git_iterator *iterator_given_or_empty(git_iterator **empty, git_iterator *given)
+{
+	if (given)
+		return given;
+
+	if (git_iterator_for_nothing(empty, GIT_ITERATOR_DONT_IGNORE_CASE, NULL, NULL) < 0)
+		return NULL;
+
+	return *empty;
+}
+
+int git_merge__iterators(
 	git_index **out,
 	git_repository *repo,
-	const git_tree *ancestor_tree,
-	const git_tree *our_tree,
-	const git_tree *their_tree,
+	git_iterator *ancestor_iter,
+	git_iterator *our_iter,
+	git_iterator *theirs_iter,
 	const git_merge_options *given_opts)
 {
+	git_iterator *empty_ancestor = NULL,
+		*empty_ours = NULL,
+		*empty_theirs = NULL;
 	git_merge_diff_list *diff_list;
 	git_merge_options opts;
 	git_merge_diff *conflict;
@@ -1772,11 +1778,12 @@ int git_merge_trees(
 	size_t i;
 	int error = 0;
 
-	assert(out && repo && (our_tree || their_tree));
+	assert(out && repo);
 
 	*out = NULL;
 
-	GITERR_CHECK_VERSION(given_opts, GIT_MERGE_OPTIONS_VERSION, "git_merge_options");
+	GITERR_CHECK_VERSION(
+		given_opts, GIT_MERGE_OPTIONS_VERSION, "git_merge_options");
 
 	if ((error = merge_normalize_opts(repo, &opts, given_opts)) < 0)
 		return error;
@@ -1784,7 +1791,12 @@ int git_merge_trees(
 	diff_list = git_merge_diff_list__alloc(repo);
 	GITERR_CHECK_ALLOC(diff_list);
 
-	if ((error = git_merge_diff_list__find_differences(diff_list, ancestor_tree, our_tree, their_tree)) < 0 ||
+	ancestor_iter = iterator_given_or_empty(&empty_ancestor, ancestor_iter);
+	our_iter = iterator_given_or_empty(&empty_ours, our_iter);
+	theirs_iter = iterator_given_or_empty(&empty_theirs, theirs_iter);
+
+	if ((error = git_merge_diff_list__find_differences(
+			diff_list, ancestor_iter, our_iter, theirs_iter)) < 0 ||
 		(error = git_merge_diff_list__find_renames(repo, diff_list, &opts)) < 0)
 		goto done;
 
@@ -1808,10 +1820,44 @@ int git_merge_trees(
 
 done:
 	git_merge_diff_list__free(diff_list);
+	git_iterator_free(empty_ancestor);
+	git_iterator_free(empty_ours);
+	git_iterator_free(empty_theirs);
+
+	return error;
+}
+
+int git_merge_trees(
+	git_index **out,
+	git_repository *repo,
+	const git_tree *ancestor_tree,
+	const git_tree *our_tree,
+	const git_tree *their_tree,
+	const git_merge_options *merge_opts)
+{
+	git_iterator *ancestor_iter = NULL, *our_iter = NULL, *their_iter = NULL;
+	int error;
+
+	if ((error = git_iterator_for_tree(&ancestor_iter, (git_tree *)ancestor_tree,
+			GIT_ITERATOR_DONT_IGNORE_CASE, NULL, NULL)) < 0 ||
+		(error = git_iterator_for_tree(&our_iter, (git_tree *)our_tree,
+			GIT_ITERATOR_DONT_IGNORE_CASE, NULL, NULL)) < 0 ||
+		(error = git_iterator_for_tree(&their_iter, (git_tree *)their_tree,
+			GIT_ITERATOR_DONT_IGNORE_CASE, NULL, NULL)) < 0)
+		goto done;
+
+	error = git_merge__iterators(
+		out, repo, ancestor_iter, our_iter, their_iter, merge_opts);
+
+done:
+	git_iterator_free(ancestor_iter);
+	git_iterator_free(our_iter);
+	git_iterator_free(their_iter);
 
 	return error;
 }
 
+
 int git_merge_commits(
 	git_index **out,
 	git_repository *repo,
diff --git a/src/merge.h b/src/merge.h
index fe4505f8b..3caf617c6 100644
--- a/src/merge.h
+++ b/src/merge.h
@@ -10,6 +10,7 @@
 #include "vector.h"
 #include "commit_list.h"
 #include "pool.h"
+#include "iterator.h"
 
 #include "git2/merge.h"
 #include "git2/types.h"
@@ -121,10 +122,11 @@ int git_merge__bases_many(
 
 git_merge_diff_list *git_merge_diff_list__alloc(git_repository *repo);
 
-int git_merge_diff_list__find_differences(git_merge_diff_list *merge_diff_list,
-	const git_tree *ancestor_tree,
-	const git_tree *ours_tree,
-	const git_tree *theirs_tree);
+int git_merge_diff_list__find_differences(
+	git_merge_diff_list *merge_diff_list,
+	git_iterator *ancestor_iterator,
+	git_iterator *ours_iter,
+	git_iterator *theirs_iter);
 
 int git_merge_diff_list__find_renames(git_repository *repo, git_merge_diff_list *merge_diff_list, const git_merge_options *opts);
 
@@ -138,6 +140,14 @@ int git_merge__setup(
 	const git_annotated_commit *heads[],
 	size_t heads_len);
 
+int git_merge__iterators(
+	git_index **out,
+	git_repository *repo,
+	git_iterator *ancestor_iter,
+	git_iterator *our_iter,
+	git_iterator *their_iter,
+	const git_merge_options *given_opts);
+
 int git_merge__check_result(git_repository *repo, git_index *index_new);
 
 int git_merge__append_conflicts_to_merge_msg(git_repository *repo, git_index *index);
diff --git a/src/stash.c b/src/stash.c
index 8aa48cafe..c79068edf 100644
--- a/src/stash.c
+++ b/src/stash.c
@@ -8,6 +8,7 @@
 #include "common.h"
 #include "repository.h"
 #include "commit.h"
+#include "message.h"
 #include "tree.h"
 #include "reflog.h"
 #include "git2/diff.h"
@@ -16,7 +17,11 @@
 #include "git2/checkout.h"
 #include "git2/index.h"
 #include "git2/transaction.h"
+#include "git2/merge.h"
+#include "index.h"
 #include "signature.h"
+#include "iterator.h"
+#include "merge.h"
 
 static int create_error(int error, const char *msg)
 {
@@ -49,23 +54,14 @@ static int append_abbreviated_oid(git_buf *out, const git_oid *b_commit)
 
 static int append_commit_description(git_buf *out, git_commit* commit)
 {
-	const char *message;
-	size_t pos = 0, len;
+	const char *summary = git_commit_summary(commit);
+	GITERR_CHECK_ALLOC(summary);
 
 	if (append_abbreviated_oid(out, git_commit_id(commit)) < 0)
 		return -1;
 
-	message = git_commit_message(commit);
-	len = strlen(message);
-
-	/* TODO: Replace with proper commit short message
-	 * when git_commit_message_short() is implemented.
-	 */
-	while (pos < len && message[pos] != '\n')
-		pos++;
-
 	git_buf_putc(out, ' ');
-	git_buf_put(out, message, pos);
+	git_buf_puts(out, summary);
 	git_buf_putc(out, '\n');
 
 	return git_buf_oom(out) ? -1 : 0;
@@ -110,7 +106,7 @@ static int build_tree_from_index(git_tree **out, git_index *index)
 	git_oid i_tree_oid;
 
 	if ((error = git_index_write_tree(&i_tree_oid, index)) < 0)
-		return -1;
+		return error;
 
 	return git_tree_lookup(out, git_index_owner(index), &i_tree_oid);
 }
@@ -553,6 +549,286 @@ cleanup:
 	return error;
 }
 
+static int retrieve_stash_commit(
+	git_commit **commit,
+	git_repository *repo,
+	size_t index)
+{
+	git_reference *stash = NULL;
+	git_reflog *reflog = NULL;
+	int error;
+	size_t max;
+	const git_reflog_entry *entry;
+
+	if ((error = git_reference_lookup(&stash, repo, GIT_REFS_STASH_FILE)) < 0)
+		goto cleanup;
+
+	if ((error = git_reflog_read(&reflog, repo, GIT_REFS_STASH_FILE)) < 0)
+		goto cleanup;
+
+	max = git_reflog_entrycount(reflog);
+	if (!max || index > max - 1) {
+		error = GIT_ENOTFOUND;
+		giterr_set(GITERR_STASH, "No stashed state at position %" PRIuZ, index);
+		goto cleanup;
+	}
+
+	entry = git_reflog_entry_byindex(reflog, index);
+	if ((error = git_commit_lookup(commit, repo, git_reflog_entry_id_new(entry))) < 0)
+		goto cleanup;
+
+cleanup:
+	git_reference_free(stash);
+	git_reflog_free(reflog);
+	return error;
+}
+
+static int retrieve_stash_trees(
+	git_tree **out_stash_tree,
+	git_tree **out_base_tree,
+	git_tree **out_index_tree,
+	git_tree **out_index_parent_tree,
+	git_tree **out_untracked_tree,
+	git_commit *stash_commit)
+{
+	git_tree *stash_tree = NULL;
+	git_commit *base_commit = NULL;
+	git_tree *base_tree = NULL;
+	git_commit *index_commit = NULL;
+	git_tree *index_tree = NULL;
+	git_commit *index_parent_commit = NULL;
+	git_tree *index_parent_tree = NULL;
+	git_commit *untracked_commit = NULL;
+	git_tree *untracked_tree = NULL;
+	int error;
+
+	if ((error = git_commit_tree(&stash_tree, stash_commit)) < 0)
+		goto cleanup;
+
+	if ((error = git_commit_parent(&base_commit, stash_commit, 0)) < 0)
+		goto cleanup;
+	if ((error = git_commit_tree(&base_tree, base_commit)) < 0)
+		goto cleanup;
+
+	if ((error = git_commit_parent(&index_commit, stash_commit, 1)) < 0)
+		goto cleanup;
+	if ((error = git_commit_tree(&index_tree, index_commit)) < 0)
+		goto cleanup;
+
+	if ((error = git_commit_parent(&index_parent_commit, index_commit, 0)) < 0)
+		goto cleanup;
+	if ((error = git_commit_tree(&index_parent_tree, index_parent_commit)) < 0)
+		goto cleanup;
+
+	if (git_commit_parentcount(stash_commit) == 3) {
+		if ((error = git_commit_parent(&untracked_commit, stash_commit, 2)) < 0)
+			goto cleanup;
+		if ((error = git_commit_tree(&untracked_tree, untracked_commit)) < 0)
+			goto cleanup;
+	}
+
+	*out_stash_tree = stash_tree;
+	*out_base_tree = base_tree;
+	*out_index_tree = index_tree;
+	*out_index_parent_tree = index_parent_tree;
+	*out_untracked_tree = untracked_tree;
+
+cleanup:
+	git_commit_free(untracked_commit);
+	git_commit_free(index_parent_commit);
+	git_commit_free(index_commit);
+	git_commit_free(base_commit);
+	if (error < 0) {
+		git_tree_free(stash_tree);
+		git_tree_free(base_tree);
+		git_tree_free(index_tree);
+		git_tree_free(index_parent_tree);
+		git_tree_free(untracked_tree);
+	}
+	return error;
+}
+
+static int merge_index_and_tree(
+	git_index **out,
+	git_repository *repo,
+	git_tree *ancestor_tree,
+	git_index *ours_index,
+	git_tree *theirs_tree)
+{
+	git_iterator *ancestor = NULL, *ours = NULL, *theirs = NULL;
+	const git_iterator_flag_t flags = GIT_ITERATOR_DONT_IGNORE_CASE;
+	int error;
+
+	if ((error = git_iterator_for_tree(&ancestor, ancestor_tree, flags, NULL, NULL)) < 0 ||
+		(error = git_iterator_for_index(&ours, ours_index, flags, NULL, NULL)) < 0 ||
+		(error = git_iterator_for_tree(&theirs, theirs_tree, flags, NULL, NULL)) < 0)
+		goto done;
+
+	error = git_merge__iterators(out, repo, ancestor, ours, theirs, NULL);
+
+done:
+	git_iterator_free(ancestor);
+	git_iterator_free(ours);
+	git_iterator_free(theirs);
+	return error;
+}
+
+static void normalize_apply_options(
+	git_stash_apply_options *opts,
+	const git_stash_apply_options *given_apply_opts)
+{	
+	if (given_apply_opts != NULL) {
+		memcpy(opts, given_apply_opts, sizeof(git_stash_apply_options));
+	} else {
+		git_stash_apply_options default_apply_opts = GIT_STASH_APPLY_OPTIONS_INIT;
+		memcpy(opts, &default_apply_opts, sizeof(git_stash_apply_options));
+	}
+
+	if ((opts->checkout_options.checkout_strategy & (GIT_CHECKOUT_SAFE | GIT_CHECKOUT_FORCE)) == 0)
+		opts->checkout_options.checkout_strategy = GIT_CHECKOUT_SAFE;
+
+	if (!opts->checkout_options.our_label)
+		opts->checkout_options.our_label = "Updated upstream";
+
+	if (!opts->checkout_options.their_label)
+		opts->checkout_options.their_label = "Stashed changes";
+}
+
+int git_stash_apply_init_options(git_stash_apply_options *opts, unsigned int version)
+{
+	GIT_INIT_STRUCTURE_FROM_TEMPLATE(
+		opts, version, git_stash_apply_options, GIT_STASH_APPLY_OPTIONS_INIT);
+	return 0;
+}
+
+#define NOTIFY_PROGRESS(opts, progress_type) \
+	if ((opts).progress_cb && \
+		(error = (opts).progress_cb((progress_type), (opts).progress_payload))) \
+		return (error < 0) ? error : -1;
+
+int git_stash_apply(
+	git_repository *repo,
+	size_t index,
+	const git_stash_apply_options *given_opts)
+{
+	git_stash_apply_options opts;
+	unsigned int checkout_strategy;
+	git_commit *stash_commit = NULL;
+	git_tree *stash_tree = NULL;
+	git_tree *stash_parent_tree = NULL;
+	git_tree *index_tree = NULL;
+	git_tree *index_parent_tree = NULL;
+	git_tree *untracked_tree = NULL;
+	git_index *repo_index = NULL;
+	git_index *unstashed_index = NULL;
+	git_index *modified_index = NULL;
+	git_index *untracked_index = NULL;
+	int error;
+
+	GITERR_CHECK_VERSION(given_opts, GIT_STASH_APPLY_OPTIONS_VERSION, "git_stash_apply_options");
+
+	normalize_apply_options(&opts, given_opts);
+	checkout_strategy = opts.checkout_options.checkout_strategy;
+
+	NOTIFY_PROGRESS(opts, GIT_STASH_APPLY_PROGRESS_LOADING_STASH);
+
+	/* Retrieve commit corresponding to the given stash */
+	if ((error = retrieve_stash_commit(&stash_commit, repo, index)) < 0)
+		goto cleanup;
+
+	/* Retrieve all trees in the stash */
+	if ((error = retrieve_stash_trees(
+			&stash_tree, &stash_parent_tree, &index_tree,
+			&index_parent_tree, &untracked_tree, stash_commit)) < 0)
+		goto cleanup;
+
+	/* Load repo index */
+	if ((error = git_repository_index(&repo_index, repo)) < 0)
+		goto cleanup;
+
+	NOTIFY_PROGRESS(opts, GIT_STASH_APPLY_PROGRESS_ANALYZE_INDEX);
+
+	/* Restore index if required */
+	if ((opts.flags & GIT_STASH_APPLY_REINSTATE_INDEX) &&
+		git_oid_cmp(git_tree_id(stash_parent_tree), git_tree_id(index_tree))) {
+
+		if ((error = merge_index_and_tree(
+				&unstashed_index, repo, index_parent_tree, repo_index, index_tree)) < 0)
+			goto cleanup;
+
+		if (git_index_has_conflicts(unstashed_index)) {
+			error = GIT_EMERGECONFLICT;
+			goto cleanup;
+		}
+	}
+
+	NOTIFY_PROGRESS(opts, GIT_STASH_APPLY_PROGRESS_ANALYZE_MODIFIED);
+
+	/* Restore modified files in workdir */
+	if ((error = merge_index_and_tree(
+			&modified_index, repo, stash_parent_tree, repo_index, stash_tree)) < 0)
+		goto cleanup;
+
+	/* If applicable, restore untracked / ignored files in workdir */
+	if (untracked_tree) {
+		NOTIFY_PROGRESS(opts, GIT_STASH_APPLY_PROGRESS_ANALYZE_UNTRACKED);
+
+		if ((error = merge_index_and_tree(&untracked_index, repo, NULL, repo_index, untracked_tree)) < 0)
+			goto cleanup;
+	}
+
+	if (untracked_index) {
+		opts.checkout_options.checkout_strategy |= GIT_CHECKOUT_DONT_UPDATE_INDEX;
+
+		NOTIFY_PROGRESS(opts, GIT_STASH_APPLY_PROGRESS_CHECKOUT_UNTRACKED);
+
+		if ((error = git_checkout_index(repo, untracked_index, &opts.checkout_options)) < 0)
+			goto cleanup;
+
+		opts.checkout_options.checkout_strategy = checkout_strategy;
+	}
+
+
+	/* If there are conflicts in the modified index, then we need to actually
+	 * check that out as the repo's index.  Otherwise, we don't update the
+	 * index.
+	 */
+
+	if (!git_index_has_conflicts(modified_index))
+		opts.checkout_options.checkout_strategy |= GIT_CHECKOUT_DONT_UPDATE_INDEX;
+
+	/* Check out the modified index using the existing repo index as baseline,
+	 * so that existing modifications in the index can be rewritten even when
+	 * checking out safely.
+	 */
+	opts.checkout_options.baseline_index = repo_index;
+
+	NOTIFY_PROGRESS(opts, GIT_STASH_APPLY_PROGRESS_CHECKOUT_MODIFIED);
+
+	if ((error = git_checkout_index(repo, modified_index, &opts.checkout_options)) < 0)
+		goto cleanup;
+
+	if (unstashed_index && !git_index_has_conflicts(modified_index)) {
+		if ((error = git_index_read_index(repo_index, unstashed_index)) < 0)
+			goto cleanup;
+	}
+
+	NOTIFY_PROGRESS(opts, GIT_STASH_APPLY_PROGRESS_DONE);
+
+cleanup:
+	git_index_free(untracked_index);
+	git_index_free(modified_index);
+	git_index_free(unstashed_index);
+	git_index_free(repo_index);
+	git_tree_free(untracked_tree);
+	git_tree_free(index_parent_tree);
+	git_tree_free(index_tree);
+	git_tree_free(stash_parent_tree);
+	git_tree_free(stash_tree);
+	git_commit_free(stash_commit);
+	return error;
+}
+
 int git_stash_foreach(
 	git_repository *repo,
 	git_stash_cb callback,
@@ -620,7 +896,7 @@ int git_stash_drop(
 
 	max = git_reflog_entrycount(reflog);
 
-	if (index > max - 1) {
+	if (!max || index > max - 1) {
 		error = GIT_ENOTFOUND;
 		giterr_set(GITERR_STASH, "No stashed state at position %" PRIuZ, index);
 		goto cleanup;
@@ -651,3 +927,16 @@ cleanup:
 	git_reflog_free(reflog);
 	return error;
 }
+
+int git_stash_pop(
+	git_repository *repo,
+	size_t index,
+	const git_stash_apply_options *options)
+{
+	int error;
+
+	if ((error = git_stash_apply(repo, index, options)) < 0)
+		return error;
+
+	return git_stash_drop(repo, index);
+}