GIT: change commit date to author date

Question

Is it possible to change the commit date from my commit to the author date?

I adapted some commits and now the dates are all the same. I want to set it back to the old dates (or the author dates). Is this possible?

I am using Sourcetree so I have the git command line but I am not a pro at that. My external repository is bitbucket.

Answer 1

Short Answer:

git filter-branch --env-filter 'export GIT_COMMITTER_DATE="$GIT_AUTHOR_DATE"' 

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Explanation:

filter-branch lets you rewrite your git history. It can apply transformations to each commit or filter out commits based on certain criteria. See git filter-branch --help for a comprehensive description and usage instructions.

--env-filter allows you to set the environment variables that are present during the creation of the new history. It is evaluated for each commit separately.

Answer 2

Since git 1.6.3 git rebase has --committer-date-is-author-date for this purpose.

git rebase --committer-date-is-author-date 

Original answer:
There's no easy way to set the committer dates (edit: but see "edit 2" below). The author dates are easy to adjust (at commit time) since --date will let you specify each one as you go.

The environment variable GIT_COMMITTER_DATE can be used to force a different time stamp at the time you make the commit. Note, however, that you'd need to adjust this for each commit you "replay". The resulting new commit will have a different SHA-1 (because you've changed some bits in it, namely, the committer date field), which means you must redo all its descendent commits.

This is what git filter-branch does (re-create some, many, or all commits with changes made along the way, keeping a mapping from old SHA-1 IDs to new SHA-1 IDs and adjusting the parents of even-otherwise-untouched commit copies so that the "new" DAG of new SHA-1 IDs matches the "old" DAG in every possible way, i.e., in every way except for SHA-1 IDs and any other changes made by your filter(s)).

In other words, to do this, you must use git filter-branch to rewrite history, with all that this implies. [Edit: you can literally do it without git filter-branch, e.g., by doing it in git rebase -i instead, but the effect is the same.]

Edit 2: as eis noted in a comment (since removed), git rebase has --committer-date-is-author-date for this purpose. It still does the same history rewriting, but it's a lot more convenient than doing it with the raw git filter-branch command.