Commands executed from `git rebase --exec` can give different behavior
from within that environment than they would outside of it, due to the
fact that sequencer.c exports both GIT_DIR and GIT_WORK_TREE. For
example, if the relevant script calls something like
git -C ../otherdir log --format=%H --no-walk
the user may be surprised to find that the command above does not show a
commit hash from ../otherdir, because $GIT_DIR prevents automatic gitdir
detection and makes the -C option useless.
This is a regression in behavior from the original legacy
implemented-in-shell rebase. It is perhaps rare for it to cause
problems in practice, especially since most small problems that were
caused by this area of bugs has been fixed-up in the past in a way that
masked the particular bug observed without fixing the real underlying
problem.
An explanation of how we arrived at the current situation is perhaps
merited. The setting of GIT_DIR and GIT_WORK_TREE done by sequencer.c
arose from a sequence of historical accidents:
* When rebase was implemented as a shell command, it would call
git-sh-setup, which among other things would set GIT_DIR -- but not
export it. This meant that when rebase --exec commands were run via
/bin/sh -c "$COMMAND"
they would not inherit the GIT_DIR setting. The fact that GIT_DIR
was not set in the run $COMMAND is the behavior we'd like to restore.
* When the rebase--helper builtin was introduced to allow incrementally
replacing shell with C code, we had an implementation that was half
shell, half C. In particular, commit 18633e1a22 ("rebase -i: use the
rebase--helper builtin", 2017-02-09) added calls to
exec git rebase--helper ...
which caused rebase--helper to inherit the GIT_DIR environment
variable from the shell. git's setup would change the environment
variable from an absolute path to a relative one (".git"), but would
leave it set. This meant that when rebase --exec commands were run
via
run_command_v_opt(...)
they would inherit the GIT_DIR setting.
* In commit 09d7b6c6fa ("sequencer: pass absolute GIT_DIR to exec
commands", 2017-10-31), it was noted that the GIT_DIR caused problems
with some commands; e.g.
git rebase --exec 'cd subdir && git describe' ...
would have GIT_DIR=.git which was invalid due to the change to the
subdirectory. Instead of questioning why GIT_DIR was set, that commit
instead made sequencer change GIT_DIR to be an absolute path and
explicitly export it via
argv_array_pushf(&child_env, "GIT_DIR=%s", absolute_path(get_git_dir()));
run_command_v_opt_cd_env(..., child_env.argv)
* In commit ab5e67d751 ("sequencer: pass absolute GIT_WORK_TREE to exec
commands", 2018-07-14), it was noted that when GIT_DIR is set but
GIT_WORK_TREE is not, that we do not discover GIT_WORK_TREE but just
assume it is '.'. That is incorrect if trying to run commands from a
subdirectory. However, rather than question why GIT_DIR was set, that
commit instead also added GIT_WORK_TREE to the list of things to
export.
Each of the above problems would have been fixed automatically when
git-rebase became a full builtin, had it not been for the fact that
sequencer.c started exporting GIT_DIR and GIT_WORK_TREE in the interim.
Stop exporting them now.
Signed-off-by: Elijah Newren <newren@gmail.com>
Acked-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Acked-by: Johannes Altmanninger <aclopte@gmail.com>
Acked-by: Phillip Wood <phillip.wood123@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Git - fast, scalable, distributed revision control system
Git is a fast, scalable, distributed revision control system with an
unusually rich command set that provides both high-level operations
and full access to internals.
Git is an Open Source project covered by the GNU General Public
License version 2 (some parts of it are under different licenses,
compatible with the GPLv2). It was originally written by Linus
Torvalds with help of a group of hackers around the net.
Please read the file INSTALL for installation instructions.
Many Git online resources are accessible from https://git-scm.com/
including full documentation and Git related tools.
See Documentation/gittutorial.txt to get started, then see
Documentation/giteveryday.txt for a useful minimum set of commands, and
Documentation/git-<commandname>.txt for documentation of each command.
If git has been correctly installed, then the tutorial can also be
read with man gittutorial or git help tutorial, and the
documentation of each command with man git-<commandname> or git help <commandname>.
CVS users may also want to read Documentation/gitcvs-migration.txt
(man gitcvs-migration or git help cvs-migration if git is
installed).
Issues which are security relevant should be disclosed privately to
the Git Security mailing list git-security@googlegroups.com.
The maintainer frequently sends the "What's cooking" reports that
list the current status of various development topics to the mailing
list. The discussion following them give a good reference for
project status, development direction and remaining tasks.
The name "git" was given by Linus Torvalds when he wrote the very
first version. He described the tool as "the stupid content tracker"
and the name as (depending on your mood):
random three-letter combination that is pronounceable, and not
actually used by any common UNIX command. The fact that it is a
mispronunciation of "get" may or may not be relevant.
stupid. contemptible and despicable. simple. Take your pick from the
dictionary of slang.
"global information tracker": you're in a good mood, and it actually
works for you. Angels sing, and a light suddenly fills the room.
"goddamn idiotic truckload of sh*t": when it breaks
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