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[PATCH v3 1/3] Support multiple virtual repositories with a single object store and refs

From
Jamey Sharp <jamey@minilop.net>
Date
May 25, 2011, 00:46 UTC
Message-ID
<1306284392-12034-1-git-send-email-jamey@minilop.net>
From: Josh Triplett <josh@joshtriplett.org>

Given many repositories with copies of the same objects (such as branches of the same source), sharing a common object store will avoid duplication. Alternates provide a single baseline, but don't handle ongoing activity in the various repositories. Furthermore, operations such as git-gc need to know about all of the refs.

Git supports storing multiple virtual repositories within the object store and references of a single underlying repository. The underlying repository stores the objects for all of the virtual repositories, and includes all the refs and heads of the virtual repositories using prefixed names.

git-upload-pack and git-receive-pack rewrite the names of refs and heads as specified by the --ref-prefix and --head options. For instance, --ref-prefix=virtual/reponame/ will use refs/virtual/reponame/heads/* and refs/virtual/reponame/tags/*. git-upload-pack and git-receive-pack will ignore any references that do not match the specified prefix.

These options implement the underlying mechanism for virtual repositories; the higher-level protocol handler (such as http-backend or a custom server) can pass these options when invoking upload-pack or receive-pack, providing values based on components of the repository path. For a simple local test, git-remote-ext works:

git clone ext::'git %s --ref-prefix=virtual/reponame/ --head=virtual-HEAD/reponame storage.git'
Commit by Josh Triplett and Jamey Sharp.
Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Signed-off-by: Jamey Sharp <jamey@minilop.net>
---
v2: remove accidentally-included debug message, and add patch 2/2 for
    git-http-backend.
v3: add patch 3/3 with documentation for virtual repositories, and
    incorporated feedback from Jeff King and Junio C Hamano.
 builtin/receive-pack.c |   36 +++++++++++++++++++++++++++---------
 upload-pack.c          |   34 +++++++++++++++++++++++++++-------
 2 files changed, 54 insertions(+), 16 deletions(-)
diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
index e1ba4dc..76dacd0 100644
--- a/builtin/receive-pack.c
+++ b/builtin/receive-pack.c
@@ -34,6 +34,8 @@ static int prefer_ofs_delta = 1;
 static int auto_update_server_info;
 static int auto_gc = 1;
 static const char *head_name;
+static const char *head_path = "HEAD";
+static const char *ref_prefix = "refs/";
 static int sent_capabilities;
 
 static enum deny_action parse_deny_action(const char *var, const char *value)
@@ -108,11 +110,12 @@ static int receive_pack_config(const char *var, const char *value, void *cb)
 
 static int show_ref(const char *path, const unsigned char *sha1, int flag, void *cb_data)
 {
+	const char *refnameprefix = cb_data;
 	if (sent_capabilities)
-		packet_write(1, "%s %s\n", sha1_to_hex(sha1), path);
+		packet_write(1, "%s %s%s\n", sha1_to_hex(sha1), refnameprefix, path);
 	else
-		packet_write(1, "%s %s%c%s%s\n",
-			     sha1_to_hex(sha1), path, 0,
+		packet_write(1, "%s %s%s%c%s%s\n",
+			     sha1_to_hex(sha1), refnameprefix, path, 0,
 			     " report-status delete-refs side-band-64k",
 			     prefer_ofs_delta ? " ofs-delta" : "");
 	sent_capabilities = 1;
@@ -121,9 +124,9 @@ static int show_ref(const char *path, const unsigned char *sha1, int flag, void
 
 static void write_head_info(void)
 {
-	for_each_ref(show_ref, NULL);
+	for_each_ref_in(ref_prefix, show_ref, "refs/");
 	if (!sent_capabilities)
-		show_ref("capabilities^{}", null_sha1, 0, NULL);
+		show_ref("capabilities^{}", null_sha1, 0, "");
 
 }
 
@@ -332,6 +335,8 @@ static void refuse_unconfigured_deny_delete_current(void)
 static const char *update(struct command *cmd)
 {
 	const char *name = cmd->ref_name;
+	struct strbuf prefixed_name_buf = STRBUF_INIT;
+	const char *prefixed_name;
 	unsigned char *old_sha1 = cmd->old_sha1;
 	unsigned char *new_sha1 = cmd->new_sha1;
 	struct ref_lock *lock;
@@ -342,7 +347,10 @@ static const char *update(struct command *cmd)
 		return "funny refname";
 	}
 
-	if (is_ref_checked_out(name)) {
+	strbuf_addf(&prefixed_name_buf, "%s%s", ref_prefix, name + 5);
+	prefixed_name = strbuf_detach(&prefixed_name_buf, NULL);
+
+	if (is_ref_checked_out(prefixed_name)) {
 		switch (deny_current_branch) {
 		case DENY_IGNORE:
 			break;
@@ -370,7 +378,7 @@ static const char *update(struct command *cmd)
 			return "deletion prohibited";
 		}
 
-		if (!strcmp(name, head_name)) {
+		if (!strcmp(prefixed_name, head_name)) {
 			switch (deny_delete_current) {
 			case DENY_IGNORE:
 				break;
@@ -426,14 +434,14 @@ static const char *update(struct command *cmd)
 			rp_warning("Allowing deletion of corrupt ref.");
 			old_sha1 = NULL;
 		}
-		if (delete_ref(name, old_sha1, 0)) {
+		if (delete_ref(prefixed_name, old_sha1, 0)) {
 			rp_error("failed to delete %s", name);
 			return "failed to delete";
 		}
 		return NULL; /* good */
 	}
 	else {
-		lock = lock_any_ref_for_update(name, old_sha1, 0);
+		lock = lock_any_ref_for_update(prefixed_name, old_sha1, 0);
 		if (!lock) {
 			rp_error("failed to lock %s", name);
 			return "failed to lock";
@@ -760,6 +768,16 @@ int cmd_receive_pack(int argc, const char **argv, const char *prefix)
 				advertise_refs = 1;
 				continue;
 			}
+			if (!prefixcmp(arg, "--head=")) {
+				head_path = arg+7;
+				continue;
+			}
+			if (!prefixcmp(arg, "--ref-prefix=")) {
+				struct strbuf prefixbuf = STRBUF_INIT;
+				strbuf_addf(&prefixbuf, "refs/%s", arg+13);
+				ref_prefix = strbuf_detach(&prefixbuf, NULL);
+				continue;
+			}
 			if (!strcmp(arg, "--stateless-rpc")) {
 				stateless_rpc = 1;
 				continue;
diff --git a/upload-pack.c b/upload-pack.c
index ce5cbbe..a1e495f 100644
--- a/upload-pack.c
+++ b/upload-pack.c
@@ -34,6 +34,8 @@ static int shallow_nr;
 static struct object_array have_obj;
 static struct object_array want_obj;
 static struct object_array extra_edge_obj;
+static const char *head_path = "HEAD";
+static const char *ref_prefix = "";
 static unsigned int timeout;
 /* 0 for no sideband,
  * otherwise maximum packet size (up to 65520 bytes).
@@ -640,17 +642,18 @@ static int send_ref(const char *refname, const unsigned char *sha1, int flag, vo
 	static const char *capabilities = "multi_ack thin-pack side-band"
 		" side-band-64k ofs-delta shallow no-progress"
 		" include-tag multi_ack_detailed";
+	const char *refnameprefix = cb_data;
 	struct object *o = parse_object(sha1);
 
 	if (!o)
 		die("git upload-pack: cannot find object %s:", sha1_to_hex(sha1));
 
 	if (capabilities)
-		packet_write(1, "%s %s%c%s%s\n", sha1_to_hex(sha1), refname,
+		packet_write(1, "%s %s%s%c%s%s\n", sha1_to_hex(sha1), refnameprefix, refname,
 			     0, capabilities,
 			     stateless_rpc ? " no-done" : "");
 	else
-		packet_write(1, "%s %s\n", sha1_to_hex(sha1), refname);
+		packet_write(1, "%s %s%s\n", sha1_to_hex(sha1), refnameprefix, refname);
 	capabilities = NULL;
 	if (!(o->flags & OUR_REF)) {
 		o->flags |= OUR_REF;
@@ -659,7 +662,7 @@ static int send_ref(const char *refname, const unsigned char *sha1, int flag, vo
 	if (o->type == OBJ_TAG) {
 		o = deref_tag(o, refname, 0);
 		if (o)
-			packet_write(1, "%s %s^{}\n", sha1_to_hex(o->sha1), refname);
+			packet_write(1, "%s %s%s^{}\n", sha1_to_hex(o->sha1), refnameprefix, refname);
 	}
 	return 0;
 }
@@ -678,15 +681,24 @@ static int mark_our_ref(const char *refname, const unsigned char *sha1, int flag
 
 static void upload_pack(void)
 {
+	struct strbuf prefix = STRBUF_INIT;
+	unsigned char sha1[20];
+	int flag;
+
+	strbuf_addf(&prefix, "refs/%s", ref_prefix);
 	if (advertise_refs || !stateless_rpc) {
 		reset_timeout();
-		head_ref(send_ref, NULL);
-		for_each_ref(send_ref, NULL);
+		if (resolve_ref(head_path, sha1, 1, &flag))
+			send_ref("HEAD", sha1, flag, "");
+		for_each_ref_in(prefix.buf, send_ref, "refs/");
 		packet_flush(1);
 	} else {
-		head_ref(mark_our_ref, NULL);
-		for_each_ref(mark_our_ref, NULL);
+		if (resolve_ref(head_path, sha1, 1, &flag))
+			mark_our_ref("HEAD", sha1, flag, NULL);
+		for_each_ref_in(prefix.buf, mark_our_ref, NULL);
 	}
+	strbuf_release(&prefix);
+
 	if (advertise_refs)
 		return;
 
@@ -716,6 +728,14 @@ int main(int argc, char **argv)
 			advertise_refs = 1;
 			continue;
 		}
+		if (!prefixcmp(arg, "--head=")) {
+			head_path = arg+7;
+			continue;
+		}
+		if (!prefixcmp(arg, "--ref-prefix=")) {
+			ref_prefix = arg+13;
+			continue;
+		}
 		if (!strcmp(arg, "--stateless-rpc")) {
 			stateless_rpc = 1;
 			continue;

-- 
1.7.5.1
Next: Jamey Sharp
Message 1 of 11 in “Support multiple virtual repositories with a single object store and refs”
  1. 1/3 Support multiple virtual repositories with a single object store and refsJamey Sharp, May 25, 2011
  2. 2/3 Support virtual repositories in smart http-backend, specified by environmentJamey Sharp, May 25, 2011
  3. 3/3 Add documentation for virtual repositoriesJamey Sharp, May 25, 2011
  4. Jeff KingMay 25, 2011
  5. Shawn PearceMay 25, 2011
  6. Jeff KingMay 25, 2011
  7. Shawn PearceMay 26, 2011
  8. Junio C HamanoMay 25, 2011
  9. Josh TriplettMay 25, 2011
  10. Junio C HamanoMay 25, 2011
  11. Jamey SharpMay 25, 2011

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