Compare branches & commits

The commands for 'is this branch ahead/behind', 'what's the common ancestor', and 'what will merging this actually bring in' — gathered in one place instead of re-derived from log/diff each time.

#git #diff #log #branches

Ancestry

Common ancestor / is-ancestor

SHELL

1git merge-base branchA branchB # the commit both branches diverged from

2git merge-base --is-ancestor A B; echo $? # 0 if A is an ancestor of B

Ahead / behind

Counts

SHELL

1git rev-list --left-right --count branchA...branchB

2# <ahead>\t<behind> (left = only in A, right = only in B)

4git rev-list --count branchA..branchB # just 'ahead' (commits B has that A doesn't)

5git branch -vv # every local branch vs its upstream, ahead/behind

Content diff

What actually changed

SHELL

1git log branchA..branchB --oneline # commits branchB has that branchA doesn't

2git log branchB..branchA --oneline # commits branchA has that branchB doesn't

3git diff branchA...branchB # content diff of what branchB adds since divergence

4git diff branchA branchB --stat # size of the full diff between the two tips

Quick answers

STEP 1 OF 4

Same tree? — git diff branchA branchB --quiet; echo $? (0 = identical content)

List branches by recency

for-each-ref

SHELL

1git for-each-ref --sort=-committerdate refs/heads/ \

2 --format='%(refname:short) %(committerdate:relative)'

Note

Two-dot (A..B) is a direct set difference; three-dot (A...B) is relative to the merge-base. Mixing them up is the #1 reason a comparison looks empty or absurdly large.