rev-parse: add --prefix option

This makes 'git rev-parse' behave as if it were invoked from the
specified subdirectory of a repository, with the difference that any
file paths which it prints are prefixed with the full path from the top
of the working tree.

This is useful for shell scripts where we may want to cd to the top of
the working tree but need to handle relative paths given by the user on
the command line.

Signed-off-by: John Keeping <john@keeping.me.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 19 insertions, 5 deletions

diff --git a/builtin/rev-parse.c b/builtin/rev-parse.c
index f267a1d3b5..de894c7577 100644
--- a/builtin/rev-parse.c
+++ b/builtin/rev-parse.c
@@ -212,11 +212,17 @@ static void show_datestring(const char *flag, const char *datestr)
 	show(buffer);
 }
 
-static int show_file(const char *arg)
+static int show_file(const char *arg, int output_prefix)
 {
 	show_default();
 	if ((filter & (DO_NONFLAGS|DO_NOREV)) == (DO_NONFLAGS|DO_NOREV)) {
-		show(arg);
+		if (output_prefix) {
+			const char *prefix = startup_info->prefix;
+			show(prefix_filename(prefix,
+					     prefix ? strlen(prefix) : 0,
+					     arg));
+		} else
+			show(arg);
 		return 1;
 	}
 	return 0;
@@ -470,6 +476,7 @@ N_("git rev-parse --parseopt [options] -- [<args>...]\n"
 int cmd_rev_parse(int argc, const char **argv, const char *prefix)
 {
 	int i, as_is = 0, verify = 0, quiet = 0, revs_count = 0, type = 0;
+	int output_prefix = 0;
 	unsigned char sha1[20];
 	const char *name = NULL;
 
@@ -503,7 +510,7 @@ int cmd_rev_parse(int argc, const char **argv, const char *prefix)
 		const char *arg = argv[i];
 
 		if (as_is) {
-			if (show_file(arg) && as_is < 2)
+			if (show_file(arg, output_prefix) && as_is < 2)
 				verify_filename(prefix, arg, 0);
 			continue;
 		}
@@ -527,7 +534,7 @@ int cmd_rev_parse(int argc, const char **argv, const char *prefix)
 				as_is = 2;
 				/* Pass on the "--" if we show anything but files.. */
 				if (filter & (DO_FLAGS | DO_REVS))
-					show_file(arg);
+					show_file(arg, 0);
 				continue;
 			}
 			if (!strcmp(arg, "--default")) {
@@ -535,6 +542,13 @@ int cmd_rev_parse(int argc, const char **argv, const char *prefix)
 				i++;
 				continue;
 			}
+			if (!strcmp(arg, "--prefix")) {
+				prefix = argv[i+1];
+				startup_info->prefix = prefix;
+				output_prefix = 1;
+				i++;
+				continue;
+			}
 			if (!strcmp(arg, "--revs-only")) {
 				filter &= ~DO_NOREV;
 				continue;
@@ -754,7 +768,7 @@ int cmd_rev_parse(int argc, const char **argv, const char *prefix)
 		if (verify)
 			die_no_single_rev(quiet);
 		as_is = 1;
-		if (!show_file(arg))
+		if (!show_file(arg, output_prefix))
 			continue;
 		verify_filename(prefix, arg, 1);
 	}