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I'm reading through an old deployment script and I came across a line of bash that puzzles me.

The statement is as follows.

if [[ \\$(git log @{u}.. 2> /dev/null | tail -n1) != '' ]]; 
    then echo 'LOCAL BRANCH HAS UNCOMMITTED CHANGES.';
fi;

As far as I can tell, we're running a git log and checking to see if the output was an empty string. I could be very off, but this is why I'm asking.

git log @{u}.. 2> /dev/null | tail -n1

The above is what is the confusing part. If I run this on a local repo I get an empty string as a return value. I don't understand why though. I don't understand what the @{u}.. 2> /dev/null means. From what I understand the 2> /dev/null is redirecting the possible error into a file located at /dev/null. But what is the rest of this line doing? ie the @{u}

marcusshep
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  • Note that the shouted "UNCOMMITTED" word here is quite wrong: these are *committed* changes. They just are believed, by the local Git, not to have been submitted to the corresponding upstream branch `@{u}`. – torek Aug 09 '17 at 14:42

1 Answers1

1

As you mention 2> /dev/null redirects stderr (defined as file descriptor 2 by POSIX) to /dev/null, a common trick to ignore error messages.

@{u} is a shortcut to the upstream branch, see this answer.

git log @{u}.. is the same as git log @{u}..HEAD. Double dot specifies a range of commits, e.g. all commits in HEAD minus all commits in @{u}.

So HEAD (local branch) minus upstream branch will give you the local commits that you have not pushed yet.

Hilborn
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