How to determine the last Mercurial commit that changed file X?

Question

Given a checkout of a Mercurial repository and a filename. How does one determine the last commit that changed that file? Unlike git, care must be taken with branches. The intended semantic here is to follow the history of the branch. Where branches fork from other branches, follow parent branches.

Non-solutions:

• shows commits from unmerged branches

  hg log -l 1 filename
  

• empty output if the file remains unchanged after branch creation

  hg log -l 1 -b . filename
  

Arguably, this question highlights misuse of branches and bookmarks should be used instead. However that may be, existing history necessiates taking branches into account.

Answer 1

The -f flag tells hg log to follow history of the current or selected changeset, so this should find the first change of a file without looking at changesets that aren't direct ancestors:

hg log -f -l 1 filename