Re: What's cooking in git.git (Mar 2009, #06; Sat, 21)

From: Johannes Sixt <j6t@kdbg.org>
Date: Mar 21, 2009, 22:21 UTC
Message-ID: <200903212321.18283.j6t@kdbg.org>
In-Reply-To: <7vk56jfgt2.fsf@gitster.siamese.dyndns.org>

On Samstag, 21. März 2009, Junio C Hamano wrote:

> * js/maint-1.6.0-exec-path-env (Wed Mar 18 08:42:53 2009 +0100) 1 commit
>  - export GIT_EXEC_PATH when git is run with --exec-path

Here is the patch again with a commit message that explains what's going on.

But notice that this is probably not a complete solution: As you can see (below) from the analysis, a git-repack that was taken from $prefix would invoke a git that is not from $prefix, but from the initial command's --exec-path. I think this can be solved by installing the git executable in $prefix/libexec/git-core as well.

-- Hannes

-- 8< --
Subject: [PATCH] Propagate --exec-path setting to external commands via GIT_EXEC_PATH

Let PATH0=$PATH that was set before the invocation. Let /foo be a build directory. Let /pfx be the installation prefix. Let pfxexecpath=/pfx/libexec/git-core.

The following is going on when 'git --exec-path=/foo gc' is invoked:

1. git sets PATH=/foo:$PATH0 using the path from --exec-path

2. gc execs 'git repack' (note: no dash).

3. Since there is a git in /foo (it's a build directory), /foo/git is
   taken.

4. No explicit exec-path is set this time, hence, this secondary git sets
   PATH=$pfxexecpath:/foo:$PATH

5. Since 'repack' is not a built-in, execv_dashed_external execs
   'git-repack' (note: dash).

6. There is a $pfxexecpath/git-repack, and it is taken.

7. This git-repack runs 'git pack-objects' (note: no dash).

8. There is no git in $pfxexecpath, but there is one in /foo. Hence,
   /foo/git is run.

9. pack-objects is a builtin, hence, in effect /foo/git-pack-objects
   is run.

As you can see, the way in which we previously set the PATH allowed to mix gits of different vintage. By setting GIT_EXEC_PATH when --exec-path was given on the command line, we reduce the confusion.

Signed-off-by: Johannes Sixt <j6t@kdbg.org>
---
 exec_cmd.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/exec_cmd.c b/exec_cmd.c
index 217c125..408e4e5 100644
--- a/exec_cmd.c
+++ b/exec_cmd.c
@@ -61,6 +61,10 @@ const char *git_extract_argv0_path(const char *argv0)
 void git_set_argv_exec_path(const char *exec_path)
 {
 	argv_exec_path = exec_path;
+	/*
+	 * Propagate this setting to external programs.
+	 */
+	setenv(EXEC_PATH_ENVIRONMENT, exec_path, 1);
 }

-- 
1.6.2.1.224.g2225f