Re: [PATCH] rebase: exec leaks GIT_DIR to environment

[Phillip Wood <phillip.wood@talktalk.net>]

On 28/10/17 17:00, Johannes Schindelin wrote:
> 
> Hi Jake,
> 
> On Fri, 27 Oct 2017, Jacob Keller wrote:
> 
>> From: Jacob Keller <jacob.keller@gmail.com>
>>
>> I noticed a failure with git rebase interactive mode which causes "exec"
>> commands to be run with GIT_DIR set. When GIT_DIR is in the environment,
>> then any command which results in running a git command in
>> a subdirectory will fail because GIT_DIR=".git".
>>
>> This unfortunately breaks one of my project's Makefiles, which uses
>> git-describe to find the version information, but does so from within
>> a sub directory.
>>
>> I'm in the process of running a bisect to find where this got
>> introduced, but I suspect it's part of the rebase--helper changes that
>> happened a while ago.
> 
> A safe assumption. I do not know how the shell code managed that GIT_DIR
> reset, though:
> 
> -- snip from v2.12.0's git-rebase--interactive.sh --
>         x|"exec")
>                 read -r command rest < "$todo"
>                 mark_action_done
>                 eval_gettextln "Executing: \$rest"
>                 "${SHELL:-@SHELL_PATH@}" -c "$rest" # Actual execution
> -- snap --
> 
> Maybe you can spot it?
> 
> The fix should be as easy as
> 
> -- snip --
> diff --git a/sequencer.c b/sequencer.c
> index f2c84c2fa62..018ba8d27e2 100644
> --- a/sequencer.c
> +++ b/sequencer.c
> @@ -1859,11 +1859,13 @@ static int error_failed_squash(struct commit *commit,
>  static int do_exec(const char *command_line)
>  {
>  	const char *child_argv[] = { NULL, NULL };
> +	const char *child_env[] = { "GIT_DIR", NULL };
>  	int dirty, status;
>  
>  	fprintf(stderr, "Executing: %s\n", command_line);
>  	child_argv[0] = command_line;
> -	status = run_command_v_opt(child_argv, RUN_USING_SHELL);
> +	status = run_command_v_opt_cd_env(child_argv, RUN_USING_SHELL, NULL,
> +					  child_env);
>  
>  	/* force re-reading of the cache */
>  	if (discard_cache() < 0 || read_cache() < 0)
> -- snap --

Just clearing GIT_DIR does not match the behavior of the shell version
(tested by passing -p to avoid rebase--helper) as that passes GIT_DIR to
exec commands if it has been explicitly set. I think that users that set
GIT_DIR on the command line would expect it to be propagated to exec
commands.

$ git rebase -px'echo $GIT_DIR' @

                                                            Merge commit
'7c2f1abd64' into phil
Executing: echo $GIT_DIR

Successfully rebased and updated refs/heads/phil.

$ env GIT_DIR=.git git rebase -px'echo $GIT_DIR' @

                                                            Merge commit
'7c2f1abd64' into phil
Executing: echo $GIT_DIR
/home/phil/Documents/src/git/.git/worktrees/git-next
Successfully rebased and updated refs/heads/phil.

> *However*, your test still fails with this, as
> 
> - your added test tries to remove the directory with -ff instead of -rf
> 
> - it tries to run `git rebase --abort` afterwards, which fails with my fix
>   because there is no rebase in progress
> 
> - instead of `cd subdir && ...`, it calls `>cd subdir && ...`, which
>   causes it to abort with a "subdir: not fonud"
> 
> So I need this, too, to make it all work:
> 
> -- snip --
> diff --git a/t/t3404-rebase-interactive.sh b/t/t3404-rebase-interactive.sh
> index 60ab5136f70..967caab222a 100755
> --- a/t/t3404-rebase-interactive.sh
> +++ b/t/t3404-rebase-interactive.sh
> @@ -108,13 +108,13 @@ test_expect_success 'rebase -i with the exec command runs from tree root' '
>  	rm -fr subdir
>  '
>  
> -test_expect_failure 'rebase -i with the exec git commands in subdirs still work' '
> -	test_when_finished "rm -ff subdir" &&
> -	test_when_finished "git rebase --abort" &&
> +test_expect_success 'rebase -i with the exec git commands in subdirs still work' '
> +	test_when_finished "rm -rf subdir" &&
> +	test_when_finished "git rebase --abort || :" &&
>  	git checkout master &&
>  	mkdir subdir && (cd subdir &&
>  	set_fake_editor &&
> -	FAKE_LINES="1 exec_>cd_subdir_&&_git_rev-parse_--is-inside-work-tree" \
> +	FAKE_LINES="1 exec_cd_subdir_&&_git_rev-parse_--is-inside-work-tree" \
>  		git rebase -i HEAD^
>  	)
>  '
> -- snap --
> 
> I only had time to write these two patches, and to verify that t3404
> passes now, but not that anything else passes, neither to write a proper
> commit message.
> 
> Maybe you can take it from there?
> 
> Ciao,
> Dscho
>