Git | Commit Short Sha Length

Question

I was trying to match local build behavior to gitlab’s one. In gitlab CI there is predifined variable called CI_COMMIT_SHORT_SHA which has a value of first 8 characters of current commit. To get “short” version of current commit you could run

$ git rev-parse --short HEAD
e0c8af0

But this gives you only 7. First of all why it is 7 and how to get 8?

Answer

1. You could pass {n} to --short.

   –short[=length] Same as –verify but shortens the object name to a unique prefix with at least length characters. The minimum length is 4, the default is the effective value of the core.abbrev configuration variable (see git-config(1)).

   $ git rev-parse --short=8 HEAD
   e0c8af03
   

2. There is core.abbrev setting for git config.

   core.abbrev Set the length object names are abbreviated to. If unspecified or set to “auto”, an appropriate value is computed based on the approximate number of packed objects in your repository, which hopefully is enough for abbreviated object names to stay unique for some time. The minimum length is 4.

   $ git config core.abbrev 8
   

What I Learned

1. 7 is somewhat default for many programms

   http://manpages.ubuntu.com/manpages/precise/en/man1/git-config.1.html

   core.abbrev Set the length object names are abbreviated to. If unspecified, many commands abbreviate to 7 hexdigits, which may not be enough for abbreviated object names to stay unique for sufficiently long time.