[PATCH 02/10] revert: Propogate errors upwards from do_pick_commit

[Ramkumar Ramachandra <artagnon@gmail.com>]

Introduce error_dirty_index, based on die_dirty_index which prints
some hints, and returns an error to be handled by its caller,
do_pick_commit.  do_pick_commit, in turn, propogates the error
upwards, and the error is finally handled by cmd_cherry_pick and
cmd_revert.  Set a simple convention for error-handling as follows:
positive return values from do_pick_commit indicate conflicts, while
negative ones indicate other errors.

Mentored-by: Jonathan Nieder <jrnieder@gmail.com>
Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
---
 builtin/revert.c |   72 ++++++++++++++++++++++++++++-------------------------
 1 files changed, 38 insertions(+), 34 deletions(-)

diff --git a/builtin/revert.c b/builtin/revert.c
index f697e66..ff26856 100644
--- a/builtin/revert.c
+++ b/builtin/revert.c
@@ -266,25 +266,15 @@ static struct tree *empty_tree(void)
 	return tree;
 }
 
-static NORETURN void die_dirty_index(const char *me)
+static int error_dirty_index(const char *me)
 {
-	if (read_cache_unmerged()) {
-		die_resolve_conflict(me);
-	} else {
-		if (advice_commit_before_merge) {
-			if (action == REVERT)
-				die(_("Your local changes would be overwritten by revert.\n"
-					  "Please, commit your changes or stash them to proceed."));
-			else
-				die(_("Your local changes would be overwritten by cherry-pick.\n"
-					  "Please, commit your changes or stash them to proceed."));
-		} else {
-			if (action == REVERT)
-				die(_("Your local changes would be overwritten by revert.\n"));
-			else
-				die(_("Your local changes would be overwritten by cherry-pick.\n"));
-		}
-	}
+	if (read_cache_unmerged())
+		return error_resolve_conflict(me);
+
+	error(_("Your local changes would be overwritten by %s.\n"), me);
+	if (advice_commit_before_merge)
+		advise(_("Please, commit your changes or stash them to proceed."));
+	return -1;
 }
 
 static int fast_forward_to(const unsigned char *to, const unsigned char *from)
@@ -398,18 +388,18 @@ static int do_pick_commit(void)
 		 * to work on.
 		 */
 		if (write_cache_as_tree(head, 0, NULL))
-			die (_("Your index file is unmerged."));
+			return error(_("Your index file is unmerged."));
 	} else {
 		if (get_sha1("HEAD", head))
-			die (_("You do not have a valid HEAD"));
+			return error(_("You do not have a valid HEAD"));
 		if (index_differs_from("HEAD", 0))
-			die_dirty_index(me);
+			return error_dirty_index(me);
 	}
 	discard_cache();
 
 	if (!commit->parents) {
 		if (action == REVERT)
-			die (_("Cannot revert a root commit"));
+			return error(_("Cannot revert a root commit"));
 		parent = NULL;
 	}
 	else if (commit->parents->next) {
@@ -418,20 +408,20 @@ static int do_pick_commit(void)
 		struct commit_list *p;
 
 		if (!mainline)
-			die(_("Commit %s is a merge but no -m option was given."),
-			    sha1_to_hex(commit->object.sha1));
+			return error(_("Commit %s is a merge but no -m option was given."),
+				sha1_to_hex(commit->object.sha1));
 
 		for (cnt = 1, p = commit->parents;
 		     cnt != mainline && p;
 		     cnt++)
 			p = p->next;
 		if (cnt != mainline || !p)
-			die(_("Commit %s does not have parent %d"),
-			    sha1_to_hex(commit->object.sha1), mainline);
+			return error(_("Commit %s does not have parent %d"),
+				sha1_to_hex(commit->object.sha1), mainline);
 		parent = p->item;
 	} else if (0 < mainline)
-		die(_("Mainline was specified but commit %s is not a merge."),
-		    sha1_to_hex(commit->object.sha1));
+		return error(_("Mainline was specified but commit %s is not a merge."),
+			sha1_to_hex(commit->object.sha1));
 	else
 		parent = commit->parents->item;
 
@@ -441,12 +431,12 @@ static int do_pick_commit(void)
 	if (parent && parse_commit(parent) < 0)
 		/* TRANSLATORS: The first %s will be "revert" or
 		   "cherry-pick", the second %s a SHA1 */
-		die(_("%s: cannot parse parent commit %s"),
-		    me, sha1_to_hex(parent->object.sha1));
+		return error(_("%s: cannot parse parent commit %s"),
+			me, sha1_to_hex(parent->object.sha1));
 
 	if (get_message(commit->buffer, &msg) != 0)
-		die(_("Cannot get commit message for %s"),
-				sha1_to_hex(commit->object.sha1));
+		return error(_("Cannot get commit message for %s"),
+			sha1_to_hex(commit->object.sha1));
 
 	/*
 	 * "commit" is an existing commit.  We would want to apply
@@ -594,14 +584,28 @@ static int revert_or_cherry_pick(int argc, const char **argv)
 
 int cmd_revert(int argc, const char **argv, const char *prefix)
 {
+	int res;
 	if (isatty(0))
 		edit = 1;
 	action = REVERT;
-	return revert_or_cherry_pick(argc, argv);
+	res = revert_or_cherry_pick(argc, argv);
+	if (res > 0)
+		/* Exit status from conflict */
+		return res;
+	if (res < 0)
+		/* Other error */
+		exit(128);
+	return 0;
 }
 
 int cmd_cherry_pick(int argc, const char **argv, const char *prefix)
 {
+	int res;
 	action = CHERRY_PICK;
-	return revert_or_cherry_pick(argc, argv);
+	res = revert_or_cherry_pick(argc, argv);
+	if (res > 0)
+		return res;
+	if (res < 0)
+		exit(128);
+	return 0;
 }
-- 
1.7.5.GIT