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From: Jeff King <>
To: "Σταύρος Ντέντος" <>
Cc: git <>
Subject: Re: Git alias syntax help
Date: Tue, 14 Jan 2020 17:28:02 -0500
Message-ID: <> (raw)
In-Reply-To: <>

On Tue, Jan 14, 2020 at 05:21:20PM +0200, Σταύρος Ντέντος wrote:

> I am having an issue with git-aliases - specifically, the intricacies
> involved in their syntax.
> In general, the syntax is confusing to me, especially when it is
> _wise_ to use quotes inside a `!sh` alias.
> e.g. which one would be the correct one
> new = "!f() { : git log ; git log \"${1}@{1}..${1}@{0}\" \"$@\" ; } ; f"
> new = !f() { : git log ; git log "${1}@{1}..${1}@{0}" "$@" ; } ; f

Only the first one is correct. In addition to the quotes in the second
one being eaten by the config parser, the unquoted semicolon starts a

> The alias confusing me is more specifically this:
> diffsort = !sh -c 'git diff "$@" | grep "^[+-]" | sort --key=1.2 | uniq -u -s1'
> The output of:
> $  colordiff -su <(git diffsort HEAD^..HEAD) <(git diffsort HEAD^^..HEAD^)
> Files /dev/fd/63 and /dev/fd/62 are identical
> is a little unexpected, since I know for a fact that one of the
> referced commits is not a code block moved.

The issue here isn't with Git's alias mechanism, but a quirk of how "sh
-c" works.  You can run with GIT_TRACE to see what we're passing to the
shell (though note that your double-quotes don't make it through):

  $ GIT_TRACE=1 git diffsort HEAD^..HEAD
  17:22:47.644542 [pid=3959333] git.c:708           trace: exec: git-diffsort HEAD^..HEAD
  17:22:47.644648 [pid=3959333] run-command.c:663   trace: run_command: git-diffsort HEAD^..HEAD
  17:22:47.645038 [pid=3959333] run-command.c:663   trace: run_command: 'sh -c '\''git diff $@ | grep ^[+-] | sort --key=1.2 | uniq -u -s1'\''' HEAD^..HEAD
  17:22:47.650319 [pid=3959336] git.c:439           trace: built-in: git diff

The problem is that "sh -c" takes the first non-option argument as $0,
not $1. For example:

  $ sh -c 'echo 0=$0, @=$@' foo bar baz
  0=foo, @=bar baz

You can add any extra string there to become $0, like:

  diffsort = "!sh -c 'git diff \"$@\" | grep \"^[+-]\" | sort --key=1.2 | uniq -u -s1' --"

which will do what you want. You can use whatever string you like, since
you know that your "-c" snippet does not ever look at $0.


  reply index

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-14 15:21 Σταύρος Ντέντος
2020-01-14 22:28 ` Jeff King [this message]
2020-01-14 23:13   ` Σταύρος Ντέντος
2020-01-15 18:13     ` Jeff King
2020-03-28 17:05       ` Philip Oakley

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