In my repo, how long must the longest hash prefix be to prevent any overlap?

Question

The --abbrev-commit flag can be used in conjunction with git log and git rev-list in order to show partial prefixes instead of the ful

Answer 1

The following shell script, when run in a local repo, prints the length of the longest prefix required to prevent any overlap among all prefix hashes of commit objects of that repository.

MAX_LENGTH=4;

git rev-list --abbrev=4 --abbrev-commit --all | \
  ( while read -r line; do
      if [ ${#line} -gt $MAX_LENGTH ]; then
        MAX_LENGTH=${#line};
      fi
    done && printf %s\\n "$MAX_LENGTH"
  )

The last time I edited this answer, the script printed

• "9" when run in a clone of the Git-project repo,
• "9" when run in a clone of the OpenStack repo,
• "11" when run in a clone of the Linux-kernel repo.