git rev-parse

git rev-parse is Git's dictionary. It understands every form of commit and ref notation, and converts them to a single canonical SHA.

Basic form

git rev-parse HEAD

# a1b2c3d4e5f6a7b8c9d0e1f2a3b4c5d6e7f8a9b0

git rev-parse main

# 7c8d9e0f1a2b3c4d5e6f7a8b9c0d1e2f3a4b5c6d

If the name is ambiguous, it returns an error. If the name does not exist, the exit code is non-zero.

Ref syntax

Utility modes

Beyond translating names to SHAs, rev-parse has several practical modes:

git rev-parse --show-toplevel

# /home/user/project           <- repository root

git rev-parse --git-dir

# /home/user/project/.git      <- where .git/ lives

git rev-parse --abbrev-ref HEAD

# main                          <- current branch name

git rev-parse --short HEAD

# a1b2c3d                       <- short unique SHA

git rev-parse --is-inside-work-tree

# true                          <- are we inside a repository?

--show-toplevel is especially useful in scripts and git hooks: it returns the repository root from any subdirectory.

In scripts

Capture the current commit SHA:

CURRENT=$(git rev-parse HEAD)

Check that you are inside a repository:

if git rev-parse --git-dir > /dev/null 2>&1; then

  echo "this is a git repo"

fi

Get the current branch name (without refs/heads/):

BRANCH=$(git rev-parse --abbrev-ref HEAD)

These are standard patterns in bash scripts that work with Git.

Pitfalls

• HEAD^ and HEAD~1 are the same thing. But HEAD^2 is not the same as HEAD~2: the first is the second parent of a merge commit; the second is two commits back along the first parent.
• git rev-parse <tag> on an annotated tag returns the SHA of the tag object, not the commit. If you need the commit, use <tag>^{commit}.
• On an empty repository, git rev-parse HEAD returns an error because HEAD does not point to anything yet.