git-describe: --long shows the object name even for a tagged commit

This is useful when you want to see parts of the commit object name
in "describe" output, even when the commit in question happens to be
a tagged version.  Instead of just emitting the tag name, it will
describe such a commit as v1.2-0-deadbeef (0th commit since tag v1.2
that points at object deadbeef....).

Signed-off-by: Santi Béjar <sbejar@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-describe.txt

@@ -51,6 +51,15 @@ OPTIONS
 	being employed to standard error.  The tag name will still
 	be printed to standard out.
 
+--long::
+	Always output the long format (the tag, the number of commits
+	and the abbreviated commit name) even when it matches a tag.
+	This is useful when you want to see parts of the commit object name
+	in "describe" output, even when the commit in question happens to be
+	a tagged version.  Instead of just emitting the tag name, it will
+	describe such a commit as v1.2-0-deadbeef (0th commit since tag v1.2
+	that points at object deadbeef....).
+
 --match <pattern>::
 	Only consider tags matching the given pattern (can be used to avoid
 	leaking private tags made from the repository).

builtin-describe.c

@@ -17,6 +17,7 @@ static const char * const describe_usage[] = {
 static int debug;	/* Display lots of verbose info */
 static int all;	/* Default to annotated tags only */
 static int tags;	/* But allow any tags if --tags is specified */
+static int longformat;
 static int abbrev = DEFAULT_ABBREV;
 static int max_candidates = 10;
 const char *pattern = NULL;
@@ -155,7 +156,11 @@ static void describe(const char *arg, int last_one)
 
 	n = cmit->util;
 	if (n) {
-		printf("%s\n", n->path);
+		if (!longformat)
+			printf("%s\n", n->path);
+		else
+			printf("%s-0-g%s\n", n->path,
+				find_unique_abbrev(cmit->object.sha1, abbrev));
 		return;
 	}
 
@@ -254,6 +259,7 @@ int cmd_describe(int argc, const char **argv, const char *prefix)
 		OPT_BOOLEAN(0, "debug",      &debug, "debug search strategy on stderr"),
 		OPT_BOOLEAN(0, "all",        &all, "use any ref in .git/refs"),
 		OPT_BOOLEAN(0, "tags",       &tags, "use any tag in .git/refs/tags"),
+		OPT_BOOLEAN(0, "long",       &longformat, "always use long format"),
 		OPT__ABBREV(&abbrev),
 		OPT_INTEGER(0, "candidates", &max_candidates,
 			    "consider <n> most recent tags (default: 10)"),
@@ -270,6 +276,9 @@ int cmd_describe(int argc, const char **argv, const char *prefix)
 
 	save_commit_buffer = 0;
 
+	if (longformat && abbrev == 0)
+		die("--long is incompatible with --abbrev=0");
+
 	if (contains) {
 		const char **args = xmalloc((6 + argc) * sizeof(char*));
 		int i = 0;

t/t6120-describe.sh

@@ -94,4 +94,6 @@ check_describe D-* --tags HEAD^^
 check_describe A-* --tags HEAD^^2
 check_describe B --tags HEAD^^2^
 
+check_describe B-0-* --long HEAD^^2^
+
 test_done