How to git commit nothing without an error?

Question

I'm trying to write a fabric script that does a git commit; however, if there is nothing to commit, git exits with a status of 1. The deploy script takes that as unsuccessful, and quits. I do want to detect actual failures-to-commit, so I can't just give fabric a blanket ignore for git commit failures. How can I allow empty-commit failures to be ignored so that deploy can continue, but still catch errors caused when a real commit fails?

def commit():
    local("git add -p && git commit")

score 241 · Accepted Answer · edited Dec 21 '22 at 13:08

241

Catch this condition beforehand by checking the exit code of git diff-index?

For example (in shell):

git add -A
git diff-index --quiet HEAD || git commit -m 'bla'

EDIT: Fixed git diff command according to Holger's comment.

edited Dec 21 '22 at 13:08

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answered Nov 14 '11 at 15:27

Tobi

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Note that `git diff` is a "porcelain" command that should not be used for scripting. What you most likely want is `git diff-index --quiet HEAD || git commit -m 'bla'`. See also [this answer](http://stackoverflow.com/a/2659808/659002). – Holger Feb 14 '13 at 01:19
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To explain things further, the problem with `git diff --quiet --exit-code --cached` is that it will evaluate to `1` (false) only for modified files that have not been staged for commit (unadded files). The up-voted comment is the best solution to account for new files and deletions. – Jorge Bucaran Dec 10 '14 at 09:21
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The comment about `git diff-index --quiet HEAD || git commit -m 'bla'` should be an answer in this question. – Rakib Sep 27 '16 at 11:52
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Since Tobi didn't care to fix his answer according to Holger's comment, I edited his answer myself. – vog Jun 07 '17 at 16:25
Note that git diff-index --quiet HEAD does not test if the local repository is up-to-date with the origin. – bortzmeyer Apr 23 '18 at 10:42
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Can someone explain what exactly is returned by "git diff-index --quiet HEAD"? Because on my system, it returns "$?=1" both when there are files staged for commit, and when there are no files staged for commit. – Erel Segal-Halevi Feb 28 '19 at 07:18
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It seems to me that `git diff-index --quiet --cached HEAD` is the correct answer. The current answer, `git diff-index --quiet HEAD` (no `--cached`), will not produce the correct result if there are differences only between the index and work tree, in which case `git commit` will fail. – Vladimir Panteleev May 08 '20 at 15:33
fyi: a related application of this concept: "git mid-edit saves": https://gist.githubusercontent.com/johnnyutahh/e8cfb515fb65635dca520117477456b8/raw – Johnny Utahh Apr 17 '22 at 23:13

score 81 · Answer 2 · edited Dec 21 '22 at 13:13

81

From the git commit man page:

--allow-empty
    Usually recording a commit that has the exact same tree as its
    sole parent commit is a mistake, and the command prevents you
    from making such a commit. This option bypasses the safety, and
    is primarily for use by foreign SCM interface scripts.

edited Dec 21 '22 at 13:13

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answered Nov 14 '11 at 15:16

Sven Marnach

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This would actually create a commit though. – ThiefMaster Nov 14 '11 at 15:17
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@ThiefMaster: Right. I can't tell from the OP whether this is a problem or not. I guess if you are using automatic commits, you do not care about your history being clean anyway. – Sven Marnach Nov 14 '11 at 15:20
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I would prefer it not to commit if it can be avoided. Is there a way to do that? – kojiro Nov 14 '11 at 15:26
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This is not answer to the question – manojlds Nov 14 '11 at 16:37
Of course the OP does not want to create an empty commit. Just that there should not be an error when an empty commit is detected. – manojlds Nov 14 '11 at 16:44
And your statement on not caring about history being clean anyway and automatic commit is wrong. OP is using `git add -p` – manojlds Nov 14 '11 at 16:45
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@manojlds: "Of course the OP does not want to create an empty commit." I left my crystal ball at home today, so I didn't know. missed the `-p`, though, but still – Sven Marnach Nov 14 '11 at 16:54
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OP may not have wanted an empty commit, but I do, thanks. – KeithWM Mar 26 '21 at 10:12

ninhjs.dev · Answer 3 · 2022-05-29T09:22:25.943

Just extending Tobi & Holger's answer with an explicit if statement.

git add -A
if ! git diff-index --quiet HEAD; then
  git commit -m "Message here"
  git push origin main
fi

Let's give it a bit explanation.

git add -A: staged your changes (required for the next step)
git diff-index --quiet HEAD will compare your staged changes with the HEAD.

--quiet is impotant as it will imply --exit-code which "makes the program exit with codes 1 if there were differences and 0 means no differences".

See --quiet.

score 3 · Answer 4 · answered Mar 18 '21 at 13:04

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When going through a shell, you can use the ... || true technique to declare a failure to be expected and ignored:

git commit -a -m "beautiful commit" || true

This would also prevent a shell script from exiting when using the errexit option.

Instead of ... || true you can also use any other command that exits with a return code of 0, such as

git commit -a -m "beautiful commit" || echo "ignore commit failure, proceed"

answered Mar 18 '21 at 13:04

Dr. Jan-Philip Gehrcke

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this wouldn't help the OP who explicitly stated that commit errors must be caught – Georg Muehlenberg Jan 26 '22 at 16:22
Gotcha. It seems like I really missed the "I can't just give fabric a blanket ignore for git commit failures" part. Looking at the exit code of `git commit` is not enough, clearly. – Dr. Jan-Philip Gehrcke Jan 27 '22 at 17:49
Best comment here, the only one actually addressing the issue (from what I understand) – ThR37 Feb 16 '23 at 15:11

score 3 · Answer 5 · answered Nov 14 '11 at 15:25

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with settings(warn_only=True):
  run('git commit ...')

This causes fabric to ignore the failure. Has the advantage of not creating empty commits.

You can wrap it in a additional layer of with hide('warnings'): to totally suppress output, otherwise you'll get a note in the fabric output that the commit failed (but the fabfile continues to execute).

answered Nov 14 '11 at 15:25

Tyler Eaves

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OP wrote "I do want to detect *actual* failures-to-commit"; this code will hide *all* failures-to-commit. – bfontaine Dec 19 '16 at 15:16

score -7 · Answer 6 · answered Apr 22 '13 at 23:42

-7

try/catch baby!

from fabric.api import local
from fabric.colors import green


def commit(message='updates'):
    try:
        local('git add .')
        local('git commit -m "' + message + '"')
        local('git push')
        print(green('Committed and pushed to git.', bold=False))
    except:
        print(green('Done committing, likely nothing new to commit.', bold=False))

answered Apr 22 '13 at 23:42

devpascoe

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To explain why you get downvoted: There can be other errors which you want to catch. You don't want to just assume that in case of an error, it might be that nothing has to be committed. -- Also, but that's unrelated: Never use a generic `except:`, use `except Exception` or so instead. – Albert Mar 21 '14 at 08:40

How to git commit nothing without an error?

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