Notes

diff-and-compare

notation meaning
HEAD, --ours currently checked out branch
feature, origin/.. --theirs other branch

merge-base

common ancestor of two branches

git merge-base main feature

triple dots (...)

(see also 3diff)

compares the common ancestor of a and b with b.
(This is different from the "double dots" (..).)

# changes in b compared to ancestor of a & b
git diff a...b 
# with main checked out

# show the changes in feature
git diff HEAD...feature

# show the changes in _our_ branch (main) 
git diff feature...HEAD

diff3-style merge conflicts

Not only show ours and theirs, but the common ancestor as well. This helps to decide about the intent of a changes.

set via command line

git config --global merge.conflictstyle diff3

or in .gitconfig

[merge]
	conflictstyle = diff3

An example merge conflict now looks like this.

<<<<<<< HEAD
initial content
add more content on main
||||||| parent of 2deebc8 (added some more content)
initial content
=======
initial content
additional content added
>>>>>>> 2deebc8 (added some more content)
section
HEAD current head of main (with potential new changes)
parent of 2deebc8 ... where the branch got of off main (common ancestor)
2deebc8 commit on the branch to be merged

patch for (rebased) feature compared to main 

# on feature, to get latest main
git rebase -i main

git diff main > feature.patch

# apply: on main (git switch main)
patch -p1 < feature.patch
git add .
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