Simple tool to 'accept theirs' or 'accept mine' on a whole file using git

The solution is very simple. git checkout <filename> tries to check out file from the index, and therefore fails on merge.

What you need to do is (i.e. checkout a commit):

To checkout your own version you can use one of:

git checkout HEAD -- <filename>

or

git checkout --ours -- <filename>

(Warning!: If you are rebasing --ours and --theirs are swapped.)

or

git show :2:<filename> > <filename> # (stage 2 is ours)

To checkout the other version you can use one of:

git checkout test-branch -- <filename>

or

git checkout --theirs -- <filename>

or

git show :3:<filename> > <filename> # (stage 3 is theirs)

You would also need to run 'add' to mark it as resolved:

git add <filename>

Try this:

To accept theirs changes: git merge --strategy-option theirs

To accept yours: git merge --strategy-option ours

Based on Jakub's answer you can configure the following git aliases for convenience:

accept-ours = "!f() { git checkout --ours -- \"${@:-.}\"; git add -u \"${@:-.}\"; }; f"accept-theirs = "!f() { git checkout --theirs -- \"${@:-.}\"; git add -u \"${@:-.}\"; }; f"

They optionally take one or several paths of files to resolve and default to resolving everything under the current directory if none are given.

Add them to the [alias] section of your ~/.gitconfig or run

git config --global alias.accept-ours '!f() { git checkout --ours -- "${@:-.}"; git add -u "${@:-.}"; }; f'git config --global alias.accept-theirs '!f() { git checkout --theirs -- "${@:-.}"; git add -u "${@:-.}"; }; f'