How much of hash is enough for a git command

Git allows you to refer to a single commit, set of commits, or range of commits in a number of ways. They aren’t necessarily obvious but are helpful to know.

Single Revisions

You can obviously refer to any single commit by its full, 40-character SHA-1 hash, but there are more human-friendly ways to refer to commits as well. This section outlines the various ways you can refer to any commit.

Short SHA-1

Git is smart enough to figure out what commit you’re referring to if you provide the first few characters of the SHA-1 hash, as long as that partial hash is at least 4 characters long and unambiguous;

First run git log to check the record

$ git log
commit 734713bc047d87bf7eac9674765ae793478c50d3
Author: Scott Chacon <schacon@gmail.com>
Date:   Fri Jan 2 18:32:33 2009 -0800

    fixed refs handling, added gc auto, updated tests

commit d921970aadf03b3cf0e71becdaab3147ba71cdef
Merge: 1c002dd... 35cfb2b...
Author: Scott Chacon <schacon@gmail.com>
Date:   Thu Dec 11 15:08:43 2008 -0800

    Merge commit 'phedders/rdocs'

commit 1c002dd4b536e7479fe34593e72e6c6c1819e53b
Author: Scott Chacon <schacon@gmail.com>
Date:   Thu Dec 11 14:58:32 2008 -0800

    added some blame and merge stuff

In this case, say you’re interested in the commit whose hash begins with 1c002dd.... You can inspect that commit with any of the following variations of git show (assuming the shorter versions are unambiguous):

$ git show 1c002dd4b536e7479fe34593e72e6c6c1819e53b
$ git show 1c002dd4b536e7479f
$ git show 1c002d

Generally, 8 to 10 characters are more than enough to be unique within a project.

Reference

[1] https://git-scm.com/book/en/v2/Git-Tools-Revision-Selection#Short-SHA-1

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