builtin-push: add --delete as syntactic sugar for :foo

Refspecs without a source side have been reported as confusing by many.
As an alternative, this adds support for commands like:

    git push origin --delete somebranch
    git push origin --delete tag sometag

Specifically, --delete will prepend a colon to all colon-less refspecs
given on the command line, and will refuse to accept refspecs with
colons to prevent undue confusion.

Signed-off-by: Jan Krüger <jk@jk.gs>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-push.txt

@@ -91,6 +91,10 @@ nor in any Push line of the corresponding remotes file---see below).
 	will be tab-separated and sent to stdout instead of stderr.  The full
 	symbolic names of the refs will be given.
 
+--delete::
+	All listed refs are deleted from the remote repository. This is
+	the same as prefixing all refs with a colon.
+
 --tags::
 	All refs under `$GIT_DIR/refs/tags` are pushed, in
 	addition to refspecs explicitly listed on the command

builtin-push.c

@@ -15,6 +15,7 @@ static const char * const push_usage[] = {
 };
 
 static int thin;
+static int deleterefs;
 static const char *receivepack;
 
 static const char **refspec;
@@ -39,11 +40,24 @@ static void set_refspecs(const char **refs, int nr)
 			if (nr <= ++i)
 				die("tag shorthand without <tag>");
 			len = strlen(refs[i]) + 11;
-			tag = xmalloc(len);
-			strcpy(tag, "refs/tags/");
+			if (deleterefs) {
+				tag = xmalloc(len+1);
+				strcpy(tag, ":refs/tags/");
+			} else {
+				tag = xmalloc(len);
+				strcpy(tag, "refs/tags/");
+			}
 			strcat(tag, refs[i]);
 			ref = tag;
-		}
+		} else if (deleterefs && !strchr(ref, ':')) {
+			char *delref;
+			int len = strlen(ref)+1;
+			delref = xmalloc(len);
+			strcpy(delref, ":");
+			strcat(delref, ref);
+			ref = delref;
+		} else if (deleterefs)
+			die("--delete only accepts plain target ref names");
 		add_refspec(ref);
 	}
 }
@@ -179,6 +193,7 @@ int cmd_push(int argc, const char **argv, const char *prefix)
 		OPT_BIT( 0 , "all", &flags, "push all refs", TRANSPORT_PUSH_ALL),
 		OPT_BIT( 0 , "mirror", &flags, "mirror all refs",
 			    (TRANSPORT_PUSH_MIRROR|TRANSPORT_PUSH_FORCE)),
+		OPT_BOOLEAN( 0, "delete", &deleterefs, "delete refs"),
 		OPT_BOOLEAN( 0 , "tags", &tags, "push tags (can't be used with --all or --mirror)"),
 		OPT_BIT('n' , "dry-run", &flags, "dry run", TRANSPORT_PUSH_DRY_RUN),
 		OPT_BIT( 0,  "porcelain", &flags, "machine-readable output", TRANSPORT_PUSH_PORCELAIN),
@@ -192,6 +207,11 @@ int cmd_push(int argc, const char **argv, const char *prefix)
 	git_config(git_default_config, NULL);
 	argc = parse_options(argc, argv, prefix, options, push_usage, 0);
 
+	if (deleterefs && (tags || (flags & (TRANSPORT_PUSH_ALL | TRANSPORT_PUSH_MIRROR))))
+		die("--delete is incompatible with --all, --mirror and --tags");
+	if (deleterefs && argc < 2)
+		die("--delete doesn't make sense without any refs");
+
 	if (tags)
 		add_refspec("refs/tags/*");
 

t/t5516-fetch-push.sh

@@ -546,6 +546,32 @@ test_expect_success 'allow deleting an invalid remote ref' '
 
 '
 
+test_expect_success 'allow deleting a ref using --delete' '
+	mk_test heads/master &&
+	(cd testrepo && git config receive.denyDeleteCurrent warn) &&
+	git push testrepo --delete master &&
+	(cd testrepo && test_must_fail git rev-parse --verify refs/heads/master)
+'
+
+test_expect_success 'allow deleting a tag using --delete' '
+	mk_test heads/master &&
+	git tag -a -m dummy_message deltag heads/master &&
+	git push testrepo --tags &&
+	(cd testrepo && git rev-parse --verify -q refs/tags/deltag) &&
+	git push testrepo --delete tag deltag &&
+	(cd testrepo && test_must_fail git rev-parse --verify refs/tags/deltag)
+'
+
+test_expect_success 'push --delete without args aborts' '
+	mk_test heads/master &&
+	test_must_fail git push testrepo --delete
+'
+
+test_expect_success 'push --delete refuses src:dest refspecs' '
+	mk_test heads/master &&
+	test_must_fail git push testrepo --delete master:foo
+'
+
 test_expect_success 'warn on push to HEAD of non-bare repository' '
 	mk_test heads/master
 	(cd testrepo &&