[RFC PATCH] revert: Implement --abort processing

[Ramkumar Ramachandra <artagnon@gmail.com>]

To abort, perform a "rerere clear" and "reset --hard" to the ref
specified by the HEAD file introduced earlier in the series.

Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
---
 I want some feedback on this -- am I doing this right? Should I be
 re-implementing "reset --hard" like this?

 builtin/revert.c                |   84 +++++++++++++++++++++++++++++++++++++--
 t/t3510-cherry-pick-sequence.sh |   27 ++++++++++++
 2 files changed, 107 insertions(+), 4 deletions(-)

diff --git a/builtin/revert.c b/builtin/revert.c
index 8eee4d5..ae85df7 100644
--- a/builtin/revert.c
+++ b/builtin/revert.c
@@ -12,6 +12,7 @@
 #include "revision.h"
 #include "rerere.h"
 #include "merge-recursive.h"
+#include "unpack-trees.h"
 #include "refs.h"
 #include "dir.h"
 
@@ -208,8 +209,6 @@ static void parse_args(int argc, const char **argv, struct replay_opts *opts)
 				NULL);
 
 	/* Remove these when the options are actually implemented */
-	if (opts->abort_oper)
-		die("--abort is not implemented yet");
 	if (opts->skip_oper)
 		die("--skip is not implemented yet");
 	if (opts->continue_oper)
@@ -647,6 +646,44 @@ static void read_and_refresh_cache(const char *me, struct replay_opts *opts)
 	rollback_lock_file(&index_lock);
 }
 
+static int hard_reset_to_ref(unsigned char *sha1)
+{
+	struct lock_file *lock = xcalloc(1, sizeof(struct lock_file));
+	struct string_list merge_rr = STRING_LIST_INIT_DUP;
+	struct unpack_trees_options unpack_tree_opts;
+	struct tree_desc desc;
+	int fd;
+
+	/* rerere clear */
+	setup_rerere(&merge_rr, 0);
+	rerere_clear(&merge_rr);
+
+	/* Clean worktree, index */
+	read_cache_unmerged();
+
+	memset(&unpack_tree_opts, 0, sizeof(unpack_tree_opts));
+	unpack_tree_opts.head_idx = 1;
+	unpack_tree_opts.src_index = &the_index;
+	unpack_tree_opts.dst_index = &the_index;
+	unpack_tree_opts.fn = oneway_merge;
+	unpack_tree_opts.merge = 1;
+	unpack_tree_opts.update = 1;
+	unpack_tree_opts.reset = 1;
+
+	fd = hold_locked_index(lock, 1);
+	fill_tree_descriptor(&desc, sha1);
+	if (unpack_trees(1, &desc, &unpack_tree_opts) < 0)
+		return error (_("Failed to unpack trees."));
+	if (write_index(&the_index, fd) ||
+		commit_locked_index(lock))
+		return error(_("Could not write index."));
+
+	/* Update the HEAD ref */
+	if (update_ref("updating HEAD", "HEAD", sha1, NULL, 0, MSG_ON_ERR))
+		return error(_("Unable to update HEAD"));
+	return 0;
+}
+
 static void format_todo(struct strbuf *buf, struct commit_list *list,
 			struct replay_opts *opts)
 {
@@ -743,6 +780,45 @@ static int pick_commits(struct replay_opts *opts)
 	return cleanup_sequencer_dir();
 }
 
+static int process_continuation(struct replay_opts *opts)
+{
+	unsigned char sha1[20];
+	char head[40];
+	int fd;
+
+	if (opts->abort_oper) {
+		/* First, read the HEAD_FILE */
+		if (!file_exists(HEAD_FILE))
+			goto error;
+		fd = open(HEAD_FILE, O_RDONLY, 0666);
+		if (fd < 0)
+			return error(_("Could not open '%s' for reading: %s"),
+				HEAD_FILE, strerror(errno));
+		if (read_in_full(fd, head, 40) < 40 || get_sha1_hex(head, sha1) < 0) {
+			close(fd);
+			return error(_("Corrupt '%s': %s"), HEAD_FILE, strerror(errno));
+		}
+		close(fd);
+
+		if (hard_reset_to_ref(sha1) < 0)
+			/* Error already reported */
+			return -1;
+		return cleanup_sequencer_dir();
+	}
+	else if (opts->skip_oper) {
+		if (!file_exists(TODO_FILE))
+			goto error;
+	}
+	else if (opts->continue_oper) {
+		if (!file_exists(TODO_FILE))
+			goto error;
+	}
+
+	return pick_commits(opts);
+error:
+	return error(_("No %s in progress"), me);
+}
+
 int cmd_revert(int argc, const char **argv, const char *prefix)
 {
 	int res;
@@ -755,7 +831,7 @@ int cmd_revert(int argc, const char **argv, const char *prefix)
 	git_config(git_default_config, NULL);
 	me = "revert";
 	parse_args(argc, argv, &opts);
-	res = pick_commits(&opts);
+	res = process_continuation(&opts);
 	if (res > 0)
 		/* Exit status from conflict */
 		return res;
@@ -775,7 +851,7 @@ int cmd_cherry_pick(int argc, const char **argv, const char *prefix)
 	git_config(git_default_config, NULL);
 	me = "cherry-pick";
 	parse_args(argc, argv, &opts);
-	res = pick_commits(&opts);
+	res = process_continuation(&opts);
 	if (res > 0)
 		return res;
 	if (res < 0)
diff --git a/t/t3510-cherry-pick-sequence.sh b/t/t3510-cherry-pick-sequence.sh
index a2e1888..7e22898 100644
--- a/t/t3510-cherry-pick-sequence.sh
+++ b/t/t3510-cherry-pick-sequence.sh
@@ -36,4 +36,31 @@ test_expect_success 'cherry-pick cleans up sequencer directory upon success' '
 	test_must_fail test -d .git/sequencer
 '
 
+test_expect_success '--abort complains when no cherry-pick is in progress' '
+	pristine_detach initial &&
+	test_must_fail git cherry-pick --abort >actual 2>&1 &&
+	echo "error: No cherry-pick in progress" >expect &&
+	test_i18ncmp expect actual
+'
+
+test_expect_success '--abort restores HEAD after failed cherry-pick' '
+	pristine_detach initial &&
+	head=$(git rev-parse HEAD) &&
+	test_must_fail git cherry-pick base..picked &&
+	git cherry-pick --abort &&
+	newhead=$(git rev-parse HEAD) &&
+	test "$head" = "$newhead"
+'
+
+test_expect_success '--abort resets worktree and index after failed cherry-pick' '
+	pristine_detach initial &&
+	head=$(git rev-parse HEAD) &&
+	test_must_fail git cherry-pick base..picked &&
+	git add foo &&
+	git cherry-pick --abort &&
+	git update-index -q --ignore-submodules --refresh &&
+	git diff-files --quiet --ignore-submodules &&
+	git diff-index --cached --quiet --ignore-submodules HEAD --
+'
+
 test_done
-- 
1.7.5.GIT