Difference between git-log and git-whatchanged?

Question

1. Given this answer to another question, and
2. given that the man pages for both git-log and git-whatchanged say they pull from git-rev-list...

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Answer 1

I don't totally agree. Can you see merge changed files with log?

I didn't find this functionality and is very useful for to know when a file was merged in some branch, example:

file c.c in branch1 has a commit date from 1/1/2012, if you do a merge to branch2, and later would like to follow the day that that commit was introduced in branch2, can git log help? If you have the merges you could search in them with git whatchanged -m sha1