</>SnippetSearch. A little code. A lot of possibility.

Test whether one revision is an ancestor of another.

Git: merge-base --is-ancestor reports its answer through the exit status.

Shell terminal 
set -euo pipefail
if git merge-base --is-ancestor HEAD~1 HEAD; then printf "Ancestor\n"; fi

Expected output EXAMPLE

Ancestor

Details

Requires Git and Bash. Run in a disposable practice repository. The test setup below creates the starting files and commits. merge-base --is-ancestor reports its answer through the exit status. The input setup creates a disposable practice repository with a fictional local author identity. Run these examples only in that repository.

✓ Verified

Tested on Ubuntu 24.04.5 LTS · · git version 2.43.0 · git 1:2.43.0-1ubuntu7.3

Test inputs, results and environment

The exact published code ran in a dedicated Linux test container with prepared inputs. Snippet process uid 65534 with a read-only root filesystem and temporary working files. Networking disabled. Fixtures and output records are isolated from the application database. Testing covers this example and its stated checks, not every input, operating system, or runtime version. The Linux container shares its host's kernel; this is not a native Windows test.

Architecture / host kernel
x86_64 / 6.18.54.1-microsoft-standard-WSL2
Snippet identity / locale
uid=65534, gid=65534 (unprivileged process) / C.UTF-8
Interpreter invocation
bash -euo pipefail -c <published code>
Container image ID
sha256:ec91410a8f6ec3e985830b5e3a0560306d36f8c1c5ccd91a6699abe707123fa3
Code SHA-256
23d52111532e5ce705b3bba96458af3f6aa3c2037c39d235acd20e08604bff63
Dependencies
git 1:2.43.0-1ubuntu7.3

Test input setup

These are the prepared inputs used by the test harness. See Details above for the prerequisites and how to run this example.

git init -q -b main
git config user.name 'Example Developer'
git config user.email 'developer@example.invalid'
git config commit.gpgsign false
git config tag.gpgsign false
git config color.ui false
printf 'first
' > note.txt
git add note.txt
git commit -qm 'Initial notes'
printf 'second\n' >> note.txt; git add note.txt; git commit -qm 'Expand notes'

Observed standard output

Ancestor

Exit code: 0. Standard error: empty. Validation: Exact stdout comparison. System-dependent values above are one recorded run.

# Git # Branches & ancestry # ancestor