Git Merge. You are in the middle of a merge. Cannot Amend.

Let’s say I made changes to branch “abc”, committed and pushed them.  This fired a build and a code-review after which the code is ready to be merged. But before these changes are merged, another party merged changes from a branch “xyz” into “abc”.

How do I replay my changes on top of changes from “xyz” in “abc” ? Here are the steps, in the root of the directory tree where the changes are located.

$ git pull origin abc
Auto-merging file1
CONFLICT (content): Merge conflict in file1
Automatic merge failed; fix conflicts and then commit the result.

At this point, I resolve the commits and attempt a git commit –amend. But this gives an error.

$ git commit --amend
fatal: You are in the middle of a merge -- cannot amend.
$ git rebase
First, rewinding head to replay your work on top of it...
Applying: change name
Using index info to reconstruct a base tree...
M file1
Falling back to patching base and 3-way merge...
Auto-merging file1
CONFLICT (content):

This shows a list of conflicting files. Find the conflicting files and edit them to resolve conflicts.

$ git rebase --continue
file: needs merge
You must edit all merge conflicts and then
mark them as resolved using git add

$ git add file1 file2
$ git rebase --continue
Applying: change name
$ git commit --amend
$ git push origin HEAD:refs/for/abc

Here’s the git rebase doc for reference. The rebase command is composed of multiple cherry-pick commands. Cherry-pick is a change-parent operation and changes commit-id = hash(parent-commit-id + changes). Here it re-chains my commit on top of a different commit than the one I started with. The commit –amend would not have changed the commit-id, and so it would not change the parent, so it fails.

Some idempotent (safe) and useful git commands.

$ git reflog [--date=iso] | or, git log -g --abbrev-commit --pretty=oneline 'HEAD@{now}'
$ git show 
$ git branch [-a]
$ git config --list
$ git remote -v
$ git fetch --dry-run

Difference between ‘origin’ and ‘upstream’ terms is explained here. An interactive git cheat sheet is here.

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