patchrebase: Fix documentation about used shell in -x

The shell used when using the -x option is the one pointed to by the SHELL_PATH constant at build time. This erroneous statement in the documentation sent me on a 10 minute wild goose chase wondering why my $SHELL was pointing to /bin/bash and my /bin/sh to dash and git was using dash and not bash.

Signed-off-by: Nikolay Borisov <nik.borisov@suse.com>
---
 Documentation/git-rebase.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

On Tue, Jan 16, 2024 at 04:18:42PM +0200, Nikolay Borisov wrote:

Good catch. It originally used $SHELL when the documentation was added in cd035b1cef (rebase -i: add exec command to launch a shell command, 2010-08-10). But that was lost when it was converted to C (which is perhaps a regression, but nobody seems to have noticed or cared until now, and at this point we should stick with the new behavior).

(I don't have an exact date since the conversion was somewhat piecemeal, but it was done by 2018).

Since then, we use the code in run-command.c's prepare_shell_cmd().

Avoiding $SHELL is obviously correct, but I think mentioning SHELL_PATH is a little hairy. It is not used on Windows; see 776297548e (Do not use SHELL_PATH from build system in prepare_shell_cmd on Windows, 2012-04-17). Maybe it makes sense to just say:

  ...in a shell (the default one, usually /bin/sh), ...

It might even make sense to just drop the parenthetical phrase entirely. Git executes lots of things using a shell, and it is always "the default one", but we don't bother saying so in most places.

-Peff

Jeff King <peff@peff.net> writes:

Thanks for your archaeological skill, as always. I like the deliberate "vagueness" of the above.

Hi

Some nitpicks since it seems like there will be another round (v2):

Lower-case “fix” is more conventional.[1]

I think anecdotes are not kept in the commit message, usually? Often they are put after the three-hyphen/three-dash line. But I didn’t manage to find any email that says that.

    The shell used when using the -x option is the one pointed to by the
    SHELL_PATH constant at build time.

    Signed-off-by: Nikolay Borisov <nik.borisov@suse.com>
    ---
      This erroneous statement in the documentation sent me on a 10 minute
      wild goose chase wondering why my $SHELL was pointing to /bin/bash and
      my /bin/sh to dash and git was using dash and not bash.

     Documentation/git-rebase.txt | 2 +-
     1 file changed, 1 insertion(+), 1 deletion(-)

† 1: SubmittingPatches:

  “ [[summary-section]]
    The title sentence after the "area:" prefix omits the full stop at the
    end, and its first word is not capitalized (the omission
    of capitalization applies only to the word after the "area:"
    prefix of the title)

"Kristoffer Haugsbakk" <code@khaugsbakk.name> writes:

Yup, that looks better. Here is what I will queue tentatively, with the improvement suggested by Peff.

----- >8 -----
Subject: [PATCH] rebase: fix documentation about used shell in -x

The shell used when using the -x option is the one pointed to by the SHELL_PATH constant at build time, not $SHELL environment variable.

We could leave the parenthetical explanation about what shell is used, but it depends on the build and platform (Windows do not even use SHELL_PATH build-time knob). Because Git executes lots of things using a shell, and it always uses the default shell, it probably is better to just stop at saying "launches the command in a shell" without going into more details.

Signed-off-by: Nikolay Borisov <nik.borisov@suse.com>
Helped-by: Jeff King <peff@peff.net>
Helped-by: Kristoffer Haugsbakk <code@khaugsbakk.name>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---

 * We could say things like

    - it is a possibility for the future to add how the default
      shell is decided (including the use of SHELL_PATH) in a more
      central part of the doucmentation like git(1)

    - at least not giving a wrong information would prevent the
      future developers wasting time on experimenting various
      settings of the $SHELL variable

   in the log message, if we want.

 Documentation/git-rebase.txt | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)