[RFC PATCH 1/1] Teach remote add the --prefix-tags option

[Wink Saville <wink@saville.com>]

When --prefix-tags is passed to `git remote add` the tagopt is set to
--prefix-tags and a second fetch line is added so tags are placed in
a separate hierarchy per remote.

For example:
  $ git remote add -f --prefix-tags gbenchmark git@github.com:google/benchmark
  Updating gbenchmark
  warning: no common commits
  remote: Counting objects: 4406, done.
  remote: Compressing objects: 100% (18/18), done.
  remote: Total 4406 (delta 7), reused 13 (delta 6), pack-reused 4382
  Receiving objects: 100% (4406/4406), 1.34 MiB | 7.58 MiB/s, done.
  Resolving deltas: 100% (2865/2865), done.
  From github.com:google/benchmark
   * [new branch]      clangtidy       -> gbenchmark/clangtidy
   * [new branch]      iter_report     -> gbenchmark/iter_report
   * [new branch]      master          -> gbenchmark/master
   * [new branch]      releasing       -> gbenchmark/releasing
   * [new branch]      reportercleanup -> gbenchmark/reportercleanup
   * [new branch]      rmheaders       -> gbenchmark/rmheaders
   * [new branch]      v2              -> gbenchmark/v2
   * [new tag]         v0.0.9          -> tags/gbenchmark/v0.0.9
   * [new tag]         v0.1.0          -> tags/gbenchmark/v0.1.0
   * [new tag]         v1.0.0          -> tags/gbenchmark/v1.0.0
   * [new tag]         v1.1.0          -> tags/gbenchmark/v1.1.0
   * [new tag]         v1.2.0          -> tags/gbenchmark/v1.2.0
   * [new tag]         v1.3.0          -> tags/gbenchmark/v1.3.0
   * [new tag]         v1.4.0          -> tags/gbenchmark/v1.4.0

And the .git/config remote "gbenchmark" section looks like:
  [remote "gbenchmark"]
    url = git@github.com:google/benchmark
    fetch = +refs/heads/*:refs/remotes/gbenchmark/*
    fetch = +refs/tags/*:refs/remotes/tags/gbenchmark/*
    tagopt = --prefix-tags

Based on a solution proposed by Junio on the email list [1]

[1]: https://public-inbox.org/git/xmqqbme51rgn.fsf@gitster-ct.c.googlers.com/T/#me7f7f153b8ba742c0dc48d8ec79c280c9682d32e

Helped-by: Junio C Hamano <gitster@pobox.com>
Helped-by: Jacob Keller <jacob.keller@gmail.com>
Signed-off-by: Wink Saville <wink@saville.com>
---
 Documentation/git-remote.txt |  8 +++++--
 builtin/remote.c             | 42 ++++++++++++++++++++++++++++++++----
 remote.c                     |  2 ++
 3 files changed, 46 insertions(+), 6 deletions(-)

diff --git a/Documentation/git-remote.txt b/Documentation/git-remote.txt
index 9659abbf8e..db0238e8bd 100644
--- a/Documentation/git-remote.txt
+++ b/Documentation/git-remote.txt
@@ -10,7 +10,7 @@ SYNOPSIS
 --------
 [verse]
 'git remote' [-v | --verbose]
-'git remote add' [-t <branch>] [-m <master>] [-f] [--[no-]tags] [--mirror=<fetch|push>] <name> <url>
+'git remote add' [-t <branch>] [-m <master>] [-f] [--tags | --prefix-tags | --no-tags] [--mirror=<fetch|push>] <name> <url>
 'git remote rename' <old> <new>
 'git remote remove' <name>
 'git remote set-head' <name> (-a | --auto | -d | --delete | <branch>)
@@ -54,7 +54,11 @@ With `-f` option, `git fetch <name>` is run immediately after
 the remote information is set up.
 +
 With `--tags` option, `git fetch <name>` imports every tag from the
-remote repository.
+remote repository to refs/tags, use --prefix-tags to import them
+to refs/remotes/tags/<name>/<tag>.
++
+With `--prefix-tags` option, `git fetch <name>` imports every tag from the
+remote repository to refs/remotes/tags/<name>/<tag>.
 +
 With `--no-tags` option, `git fetch <name>` does not import tags from
 the remote repository.
diff --git a/builtin/remote.c b/builtin/remote.c
index 5591cef775..88991f9fbe 100644
--- a/builtin/remote.c
+++ b/builtin/remote.c
@@ -14,7 +14,7 @@
 
 static const char * const builtin_remote_usage[] = {
 	N_("git remote [-v | --verbose]"),
-	N_("git remote add [-t <branch>] [-m <master>] [-f] [--tags | --no-tags] [--mirror=<fetch|push>] <name> <url>"),
+	N_("git remote add [-t <branch>] [-m <master>] [-f] [--prefix-tags | --tags | --no-tags] [--mirror=<fetch|push>] <name> <url>"),
 	N_("git remote rename <old> <new>"),
 	N_("git remote remove <name>"),
 	N_("git remote set-head <name> (-a | --auto | -d | --delete | <branch>)"),
@@ -104,7 +104,8 @@ static int fetch_remote(const char *name)
 enum {
 	TAGS_UNSET = 0,
 	TAGS_DEFAULT = 1,
-	TAGS_SET = 2
+	TAGS_SET = 2,
+	TAGS_SET_PREFIX = 3
 };
 
 #define MIRROR_NONE 0
@@ -126,6 +127,14 @@ static void add_branch(const char *key, const char *branchname,
 	git_config_set_multivar(key, tmp->buf, "^$", 0);
 }
 
+static void add_remote_tags(const char *key, const char *remotename,
+			    struct strbuf *tmp)
+{
+	strbuf_reset(tmp);
+	strbuf_addf(tmp, "+refs/tags/*:refs/remotes/tags/%s/*", remotename);
+	git_config_set_multivar(key, tmp->buf, "^$", 0);
+}
+
 static const char mirror_advice[] =
 N_("--mirror is dangerous and deprecated; please\n"
    "\t use --mirror=fetch or --mirror=push instead");
@@ -164,6 +173,9 @@ static int add(int argc, const char **argv)
 		OPT_SET_INT(0, "tags", &fetch_tags,
 			    N_("import all tags and associated objects when fetching"),
 			    TAGS_SET),
+		OPT_SET_INT(0, "prefix-tags", &fetch_tags,
+			    N_("import all tags and associated objects when fetching and prefix with <name>"),
+			    TAGS_SET_PREFIX),
 		OPT_SET_INT(0, NULL, &fetch_tags,
 			    N_("or do not fetch any tag at all (--no-tags)"), TAGS_UNSET),
 		OPT_STRING_LIST('t', "track", &track, N_("branch"),
@@ -185,6 +197,8 @@ static int add(int argc, const char **argv)
 		die(_("specifying a master branch makes no sense with --mirror"));
 	if (mirror && !(mirror & MIRROR_FETCH) && track.nr)
 		die(_("specifying branches to track makes sense only with fetch mirrors"));
+	if (mirror && (fetch_tags == TAGS_SET_PREFIX))
+		die(_("specifying a --prefix-tags makes no sense with --mirror"));
 
 	name = argv[0];
 	url = argv[1];
@@ -218,10 +232,30 @@ static int add(int argc, const char **argv)
 	}
 
 	if (fetch_tags != TAGS_DEFAULT) {
+		if (fetch_tags == TAGS_SET_PREFIX) {
+			strbuf_reset(&buf);
+			strbuf_addf(&buf, "remote.%s.fetch", name);
+			add_remote_tags(buf.buf, name, &buf2);
+		}
+
 		strbuf_reset(&buf);
 		strbuf_addf(&buf, "remote.%s.tagopt", name);
-		git_config_set(buf.buf,
-			       fetch_tags == TAGS_SET ? "--tags" : "--no-tags");
+		char *config_val = NULL;
+		switch (fetch_tags) {
+		case TAGS_UNSET:
+			config_val = "--no-tags";
+			break;
+		case TAGS_SET:
+			config_val = "--tags";
+			break;
+		case TAGS_SET_PREFIX:
+			config_val = "--prefix-tags";
+			break;
+		default:
+			die(_("Unexpected TAGS enum %d"), fetch_tags);
+			break;
+		}
+		git_config_set(buf.buf, config_val);
 	}
 
 	if (fetch && fetch_remote(name))
diff --git a/remote.c b/remote.c
index e50f7602ed..d916fda029 100644
--- a/remote.c
+++ b/remote.c
@@ -421,6 +421,8 @@ static int handle_config(const char *key, const char *value, void *cb)
 			remote->fetch_tags = -1;
 		else if (!strcmp(value, "--tags"))
 			remote->fetch_tags = 2;
+		else if (!strcmp(value, "--prefix-tags"))
+			remote->fetch_tags = -1;
 	} else if (!strcmp(subkey, "proxy")) {
 		return git_config_string((const char **)&remote->http_proxy,
 					 key, value);
-- 
2.16.2.7164.g7daebe18fb