Git

Problem

Merging or rebasing branches fails with conflict markers because the same lines were changed differently on both sides.

Symptoms

• CONFLICT (content): Merge conflict in <file>
• git status shows files as "both modified"
• <<<<<<<, =======, >>>>>>> markers appear in the file

Root Cause

Two branches modified the same lines (or one deleted a file the other modified) and Git can't automatically decide which change should win.

Solution

git status

<<<<<<< HEAD
your changes
=======
their changes
>>>>>>> branch-name

git add <file>

git merge --continue
# or
git rebase --continue

git merge --abort
# or
git rebase --abort

git mergetool

Prevention

• Pull/rebase from the target branch frequently instead of letting branches diverge for weeks
• Keep pull requests small and short-lived so overlap windows are smaller
• Agree on file/module ownership within a team to reduce simultaneous edits to the same lines
• Use git rerere to have Git remember how you resolved a conflict last time

References

• Resolving a merge conflict
• git rerere