Git is losing history/contents on individual files

Question

I work in a small company and our Git repo is a little messed up. I just did a git pull and my changes made earlier today are gone!

When I work on HEAD on the master branch, git log shows my last commit b94940c63ef965ce45b0d64ccfba4359134d2552 in its history.

Now if I do git log filename for the problematic file that lost my changes, that commit is not shown (only shows an earlier commit).

Performing git log --follow filename, my commit b94940c63ef965ce45b0d64ccfba4359134d2552 is shown as most recent.

And sure enough if I do:

git checkout b94940c63ef965ce45b0d64ccfba4359134d2552
git log filename

then the commit is shown and my changes are in the file!

In other words, the commit I made is shown in the branch history (blocking a branch merge), but individual modified files do not have that commit in their history! (unless I explicitly checkout that commit).

Questions:

1. How on earth did this happen?

2. How do I fix it? (We have problems with multiple files in our repo)

Answer 1

Alright figured out the problem. When a coworker pulled, he got some conflicts. Rather than resolving, he git reset every staged file. This was akin to doing a git checkout old_version on individual old files. So HEAD on the master ended up referring to some files that had old_version.

Now I'm manually restoring what he blew out.

Moral of story: Modifying git operations (checkout, reset, etc.) on individual files are quite dangerous.

Answer 2

This should be just a comment, but it would be hard to read. After checking out master:

git checkout master

what's the output of

git status

and

git whatchanged -m -p <path>

and

git log --graph --oneline b94940c63ef965ce45b0d64ccfba4359134d2552..master

?