diff alias which used to work in version 2.27, failing from version 2.28 onwards

Hi,

To output the diff of a specific commit, I created the alias dici (see below), git dici 12345 or git dici to output the diff of the HEAD:

[alias]
    dici = !git diff ${1:-HEAD}^..${1:-HEAD}

a trace for this alias gives (same trace for both git 2.27 and 2.28!):

14:38:45.275964 git.c:439               trace: built-in: git diff a2028e7b^..a2028e7b a2028e7b 

The commit number is put again at the end of the command (the wanted alias is supposed to output only `git diff a2028e7b^..a2028e7b`), this was accepted by version 2.27 but not by the version 2.28. For now, my temporary fix is adding a bash comment at the end of the alias:

[alias]
    dici = "!git diff ${1:-HEAD}^..${1:-HEAD} #"

Note: the first alias still doesn't work with the latest git versions (tested with 2.40.0, 2.39.2, 2.37.5).

Is that expected behavior? if yes, how is the right/clean way to discard the command line argument of the alias?

Thanks in advance!

Auriane

On Thu, Aug 24, 2023 at 10:19:18AM +0000, Reverdell  Auriane wrote:

Yes, that's expected. Your alias was always a little broken by adding the extra argument, but "git diff" got a little more careful about its input in 8bfcb3a690 (git diff: improve range handling, 2020-06-12), which as part of v2.28.

The usual way for manipulating arguments in a shell snippet is to make a function, like:

  [alias]
  dici = "!f() { git diff ${1:-HEAD}^..${1:-HEAD}; }; f"

Then Git ends up running "f a2028e7b", and the shell does the rest. It's obviously a bit more verbose to write, but you're free to do even more manipulation (e.g., using the first non-option argument as the rev and taking the rest as options).

All that said, there is a shorthand that may make your alias obsolete. From "git help revisions":

         <rev>^-<n>, e.g. HEAD^-, HEAD^-2
             Equivalent to <rev>^<n>..<rev>, with <n> = 1 if not given.

So just:

  git diff a2028e7b^-

does what you want.

-Peff

On 8/24/23, Reverdell  Auriane <auriane.reverdell@cscs.ch> wrote:

If you want to interpolate arguments in the command string, the safest way is something like dici = !sh -c 'git diff ${1:-HEAD}~..${1:-HEAD}' sh

(but why not just use git show?)

you can also use the ^! syntax instead: dici = !sh -c 'git diff ${1:-HEAD}^!' sh