57c2b6cc86
Diff output usually goes to the process stdout, but it can be redirected
with the "--output" option. We store this in the "file" pointer of
diff_options, and all of the diff code should write there instead of to
stdout.
But there's one spot we missed: running an external diff cmd. We don't
redirect its output at all, so it just defaults to the stdout of the
parent process. We should instead point its stdout at our output file.
There are a few caveats to watch out for when doing so:
- The stdout field takes a descriptor, not a FILE pointer. We can pull
out the descriptor with fileno().
- The run-command API always closes the stdout descriptor we pass to
it. So we must duplicate it (otherwise we break the FILE pointer,
since it now points to a closed descriptor).
- We don't need to worry about closing our dup'd descriptor, since the
point is that run-command will do it for us (even in the case of an
error). But we do need to make sure we skip the dup() if we set
no_stdout (because then run-command will not look at it at all).
- When the output is going to stdout, it would not be wrong to dup()
the descriptor, but we don't need to. We can skip that extra work
with a simple pointer comparison.
- It seems like you'd need to fflush() the descriptor before handing
off a copy to the child process to prevent out-of-order writes. But
that was true even before this patch! It works because run-command
always calls fflush(NULL) before running the child.
The new test shows the breakage (and fix). The need for duplicating the
descriptor doesn't need a new test; that is covered by the later test
"GIT_EXTERNAL_DIFF with more than one changed files".
Signed-off-by: Jeff King <peff@peff.net>
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.adoc to get started, then see
Documentation/giteveryday.adoc for a useful minimum set of commands, and
Documentation/git-<commandname>.adoc 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.adoc
(man gitcvs-migration or git help cvs-migration if git is
installed).
The user discussion and development of Git take place on the Git mailing list -- everyone is welcome to post bug reports, feature requests, comments and patches to git@vger.kernel.org (read Documentation/SubmittingPatches for instructions on patch submission and Documentation/CodingGuidelines).
Those wishing to help with error message, usage and informational message
string translations (localization l10) should see po/README.md
(a po file is a Portable Object file that holds the translations).
To subscribe to the list, send an email to git+subscribe@vger.kernel.org (see https://subspace.kernel.org/subscribing.html for details). The mailing list archives are available at https://lore.kernel.org/git/, https://marc.info/?l=git and other archival sites.
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