Re: [question] how can i verify whether a local branch is tracking a remote branch?

From: Jeff King <peff@peff.net>
Date: Apr 6, 2009, 04:34 UTC
Message-ID: <20090406043426.GC12341@coredump.intra.peff.net>
In-Reply-To: <4d8e3fd30904051425w6739a12fp5666e71e8b2d7958@mail.gmail.com>

On Sun, Apr 05, 2009 at 11:25:29PM +0200, Paolo Ciarrocchi wrote:

Show 10 quoted lines

> An example:
> $ git clone -n URL temp
> $ cd temp
> $ git branch -r
>   origin/master
>   origin/foo
>   Origin/bar
> $ git checkout --track -b foo origin/foo
> 
> Now, how can I know that foo is tracking origin/foo ?

Doing it right is hard. You have to:

  1. check branch.foo.merge and branch.foo.rebase; if no value, it is not
     tracking anything; if it is, remember that value as $m

  2. check branch.foo.remote for the remote name, $r

  3. check the fetch refspecs for remote $r; these can come from
     the config, or from .git/remotes/* files. Maybe even .git/branches
     files; I don't even remember how those work.

  4. find the refspec that fetches from $m; then find the matching
     destination for that refspec. That is the tracking branch.

E.g., in your example (and using a modern git):

  1. $m is refs/heads/foo
  2. $r is origin
  3. The fetch refspec is in remote.origin.fetch, and is generally
     "refs/heads/*:refs/remotes/origin/*"
  4. So refs/heads/foo becomes refs/remotes/origin/foo.
     refs/remotes/origin/foo is your tracking branch.

Steps 1 and 2 are easy, but 3 and 4 are a bit nasty. You can fake it by assuming that "refs/heads/$m" on "$r" is always "refs/remotes/$r/$m", which is true for very vanilla setups.

There is C code that does this, but there is not a good way of accessing it from the command-line. The best you can do is "git remote show origin", which on recent git versions should show something like:

  ...
  Local branches configured for 'git pull':
    foo    merges with remote foo
  ...

But of course that implies that you already guessed the remote "origin". And it's not using plumbing, so it's not very suitable for scripts.

I don't think it would be unreasonable to expose this functionality via "for-each-ref". Something like this (which would need cleanup, documentation, and perhaps a :short variant):

---

diff --git a/builtin-for-each-ref.c b/builtin-for-each-ref.c
index 5cbb4b0..3f418e4 100644
--- a/builtin-for-each-ref.c
+++ b/builtin-for-each-ref.c
@@ -8,6 +8,7 @@
 #include "blob.h"
 #include "quote.h"
 #include "parse-options.h"
+#include "remote.h"
 
 /* Quoting styles */
 #define QUOTE_NONE 0
@@ -66,6 +67,7 @@ static struct {
 	{ "subject" },
 	{ "body" },
 	{ "contents" },
+	{ "tracking" },
 };
 
 /*
@@ -699,6 +701,18 @@ static void populate_value(struct refinfo *ref)
 				v->s = s;
 			}
 		}
+		if (!strcmp(name, "tracking")) {
+			struct branch *branch;
+			if (prefixcmp(ref->refname, "refs/heads/"))
+				continue;
+			branch = branch_get(ref->refname + 11);
+			if (branch && branch->merge && branch->merge[0] &&
+			    branch->merge[0]->dst)
+				v->s = branch->merge[0]->dst;
+			else
+				v->s = NULL;
+			free(branch); /* XXX should also free other parts? */
+		}
 	}
 
 	grab_values(ref->value, 0, obj, buf, size);





> 
> Thanks.
> 
> 
> Ciao,
> -- 
> Paolo
> http://paolo.ciarrocchi.googlepages.com/
> http://mypage.vodafone.it/