[PATCH v3] Allow aliases that include other aliases

[Tim Schumacher <timschumi@gmx.de>]

Aliases can only contain non-alias git commands and their
arguments, not other user-defined aliases. Resolving further
(nested) aliases is prevented by breaking the loop after the
first alias was processed. Git then fails with a command-not-found
error.

Allow resolving nested aliases by not breaking the loop in
run_argv() after the first alias was processed. Instead, continue
incrementing `done_alias` until `handle_alias()` fails, which means that
there are no further aliases that can be processed. Prevent looping
aliases by storing substituted commands in `cmd_list` and checking if
a command has been substituted previously.

While we're at it, fix a styling issue just below the added code.
---
 git.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/git.c b/git.c
index c27c38738..64f5fbd57 100644
--- a/git.c
+++ b/git.c
@@ -674,6 +674,7 @@ static void execv_dashed_external(const char **argv)
 static int run_argv(int *argcp, const char ***argv)
 {
 	int done_alias = 0;
+	struct string_list cmd_list = STRING_LIST_INIT_NODUP;
 
 	while (1) {
 		/*
@@ -691,17 +692,23 @@ static int run_argv(int *argcp, const char ***argv)
 		/* .. then try the external ones */
 		execv_dashed_external(*argv);
 
-		/* It could be an alias -- this works around the insanity
+		if (string_list_has_string(&cmd_list, *argv[0]))
+			die(_("loop alias: %s is called twice"), *argv[0]);
+
+		string_list_append(&cmd_list, *argv[0]);
+
+		/*
+		 * It could be an alias -- this works around the insanity
 		 * of overriding "git log" with "git show" by having
 		 * alias.log = show
 		 */
-		if (done_alias)
-			break;
 		if (!handle_alias(argcp, argv))
 			break;
-		done_alias = 1;
+		done_alias++;
 	}
 
+	string_list_clear(&cmd_list, 0);
+
 	return done_alias;
 }
 
-- 
2.19.0.rc1.2.g8008c49c4.dirty