git log --merges doesn't show commits as expected

Hello!
 
(This is my first post to this mailing list and I couldn't find a FAQ section - please excuse me, if I haven't followed all the established posting guidelines yet.)

I have the following repository tree:

C
|\
| B
| /
A

Commit A: Parents=(). Initial commit. Contains file foo with content "ABC". Commit B: Parents=(A). Represents a commit on some feature branch. Contains file foo with content "XYZ". Commit C: Parents=(A, B). Represents a merge commit of a feature branch back to the main branch. Contains file foo with content "XYZ".

I expected "git log --merges foo" to show C, however, the log is empty! Specifying "--full-history" results in the correct history, therefore I assume, I misunderstand Git's default history simplification algorithm. Unfortunately, the example in the Git docs at [1] does not contain the very same situation (although it is probably one of the most common situations...).

Does anybody know why I don't see the log output I expect? I'm confused...even if the log output is correct, I don't think it follows the principle of least surprise...

Side note: specifying "--first-parent" also results in commit C being shown.

Best regards, Dominik

PS: This is a cross post of [2], somebody noted it could be a bug, which is why I decided to post to this mailing list.

[1] https://git-scm.com/docs/git-log#_history_simplification [2] http://stackoverflow.com/q/33695763/