Question

I have 10 files which have conflicts when merging branches. I’ve resolved all conflicts of the 10 files(took long time). Unfortunately before the commit, I find out that one file has been merged wrong and need start again for this file. 🙁

in the Git, How to mark the file which has been merged unmerged, in other word, how to re-merge that one file?

Answer 1

git checkout -m <filename>

This will remove it from the index, and revert back to a “conflicted” file that has all of the markers required to then do a merge.

From the git help checkout man page:

-m, --merge
    When switching branches, if you have local modifications to
    one or more files that are different between the current
    branch and the branch to which you are switching, the command
    refuses to switch branches in order to preserve your
    modifications in context. However, with this option, a
    three-way merge between the current branch, your working tree
    contents, and the new branch is done, and you will be on the
    new branch.

    When a merge conflict happens, the index entries for
    conflicting paths are left unmerged, and you need to resolve
    the conflicts and mark the resolved paths with git add (or git
    rm if the merge should result in deletion of the path).

    When checking out paths from the index, this option lets you
    recreate the conflicted merge in the specified paths.

(The last sentence is the most important one).

Here is a blog post that describes why it was added and how it is not possible with older versions of git: http://gitster.livejournal.com/43665.html