Nov 12, 2015

Git: Single Line History

You get a bug report from a user:
/usr/lib/foo/bar.rb:432:in `doit': undefined method `[]' for nil:NilClass (NoMethodError)
but in bar.rb at the line 432 there are no square brackets. The user must be using an older version of the script. Can we find out which one without asking them?

Git can help. This code will go back in history and show the line how it appeared during the past. It's a history of a single line, kind of like "git blame" but in a different dimension.

git log --format=format:%H $FILE \
| while read COMMIT_ID; do
    echo -n $COMMIT_ID:$FILE:$LINE:
    git show $COMMIT_ID:$FILE | sed -n "$LINE{p;q}"
  done \
| less 

Have I reinvented the wheel? What is its name?

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