git-branch --contains=commit

This teaches git-branch to limit its listing to branches that
are descendants to the named commit.

When you are using many topic branches, you often would want to
see which branch already includes a commit, so that you know
which can and cannot be rewound without disrupting other people.

One thing that sometimes happens to me is:

 * Somebody sends a patch that is a good maint material.  I
   apply it to 'maint':

     $ git checkout maint
     $ git am -3 -s obvious-fix.patch

 * Then somebody else sends another patch that is possibly a
   good maint material, but I'd want to cook it in 'next' to be
   extra sure.  I fork a topic from 'maint' and apply the patch:

     $ git checkout -b xx/maint-fix-foo
     $ git am -3 -s ,xx-maint-fix-foo.patch

 * A minor typo is found in the "obvious-fix.patch".

The above happens without pushing the results out, so I can
freely recover from it by amending 'maint', as long as I do not
forget to rebase the topics that were forked previously.

With this patch, I can do this to find out which topic
branches already contain the faulty commit:

    $ git branch --contains=maint^
      xx/maint-fix-foo

so I can rebase the xx/maint-fix-foo branch before merging it
to 'next'.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin-branch.c

@@ -184,9 +184,30 @@ struct ref_item {
 struct ref_list {
 	int index, alloc, maxwidth;
 	struct ref_item *list;
+	struct commit_list *with_commit;
 	int kinds;
 };
 
+static int has_commit(const unsigned char *sha1, struct commit_list *with_commit)
+{
+	struct commit *commit;
+
+	if (!with_commit)
+		return 1;
+	commit = lookup_commit_reference_gently(sha1, 1);
+	if (!commit)
+		return 0;
+	while (with_commit) {
+		struct commit *other;
+
+		other = with_commit->item;
+		with_commit = with_commit->next;
+		if (in_merge_bases(other, &commit, 1))
+			return 1;
+	}
+	return 0;
+}
+
 static int append_ref(const char *refname, const unsigned char *sha1, int flags, void *cb_data)
 {
 	struct ref_list *ref_list = (struct ref_list*)(cb_data);
@@ -206,6 +227,10 @@ static int append_ref(const char *refname, const unsigned char *sha1, int flags,
 		refname += 10;
 	}
 
+	/* Filter with with_commit if specified */
+	if (!has_commit(sha1, ref_list->with_commit))
+		return 0;
+
 	/* Don't add types the caller doesn't want */
 	if ((kind & ref_list->kinds) == 0)
 		return 0;
@@ -296,19 +321,20 @@ static void print_ref_item(struct ref_item *item, int maxwidth, int verbose,
 	}
 }
 
-static void print_ref_list(int kinds, int detached, int verbose, int abbrev)
+static void print_ref_list(int kinds, int detached, int verbose, int abbrev, struct commit_list *with_commit)
 {
 	int i;
 	struct ref_list ref_list;
 
 	memset(&ref_list, 0, sizeof(ref_list));
 	ref_list.kinds = kinds;
+	ref_list.with_commit = with_commit;
 	for_each_ref(append_ref, &ref_list);
 
 	qsort(ref_list.list, ref_list.index, sizeof(struct ref_item), ref_cmp);
 
 	detached = (detached && (kinds & REF_LOCAL_BRANCH));
-	if (detached) {
+	if (detached && has_commit(head_sha1, with_commit)) {
 		struct ref_item item;
 		item.name = xstrdup("(no branch)");
 		item.kind = REF_LOCAL_BRANCH;
@@ -505,12 +531,29 @@ static void rename_branch(const char *oldname, const char *newname, int force)
 		die("Branch is renamed, but update of config-file failed");
 }
 
+static int opt_parse_with_commit(const struct option *opt, const char *arg, int unset)
+{
+	unsigned char sha1[20];
+	struct commit *commit;
+
+	if (!arg)
+		return -1;
+	if (get_sha1(arg, sha1))
+		die("malformed object name %s", arg);
+	commit = lookup_commit_reference(sha1);
+	if (!commit)
+		die("no such commit %s", arg);
+	commit_list_insert(commit, opt->value);
+	return 0;
+}
+
 int cmd_branch(int argc, const char **argv, const char *prefix)
 {
 	int delete = 0, rename = 0, force_create = 0;
 	int verbose = 0, abbrev = DEFAULT_ABBREV, detached = 0;
 	int reflog = 0, track;
 	int kinds = REF_LOCAL_BRANCH;
+	struct commit_list *with_commit = NULL;
 
 	struct option options[] = {
 		OPT_GROUP("Generic options"),
@@ -519,6 +562,14 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 		OPT_BOOLEAN( 0 , "color",  &branch_use_color, "use colored output"),
 		OPT_SET_INT('r', NULL,     &kinds, "act on remote-tracking branches",
 			REF_REMOTE_BRANCH),
+		OPT_CALLBACK(0, "contains", &with_commit, "commit",
+			     "print only branches that contain the commit",
+			     opt_parse_with_commit),
+		{
+			OPTION_CALLBACK, 0, "with", &with_commit, "commit",
+			"print only branches that contain the commit",
+			PARSE_OPT_HIDDEN, opt_parse_with_commit,
+		},
 		OPT__ABBREV(&abbrev),
 
 		OPT_GROUP("Specific git-branch actions:"),
@@ -554,7 +605,7 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 	if (delete)
 		return delete_branches(argc, argv, delete > 1, kinds);
 	else if (argc == 0)
-		print_ref_list(kinds, detached, verbose, abbrev);
+		print_ref_list(kinds, detached, verbose, abbrev, with_commit);
 	else if (rename && (argc == 1))
 		rename_branch(head, argv[0], rename > 1);
 	else if (rename && (argc == 2))