Committing existing files to existing Git repository, while preserving timestamps

Question

The situation is this: I have a bunch of files from ages ago (back when I wasn't using source control of any kind) which I'd love to put to modern-time Git repositories.

I found one tool for this - file-fast-export. It takes existing files and spits out a file that can be fed to git fast-import. Fine so far.

Only problem is that fast-import is a bit picky about input format and file-fast-export isn't a particularly polished program - it assumes files are being imported into a new repository.

So my use case is this: I have a git repository. I discovered a previously missing subdirectory. File modification times are there. I'd need to commit each of those files on top of the current repository history so that the commit timestamps correspond to the modification times. As I understood it, Git doesn't force commits to have chronologically consecutive timestamps, only that commits follow one another. I'm happy if I can just do git log xxxxx.txt and see file history.

I'm sure there are tools that can do this. How can I do this?

Answer 1

Only problem is that fast-import is a bit picky about input format

Actually... With Git 2.28 (Q3 2020), some repositories in the wild have commits that record nonsense committer timezone (e.g. rails.git); "git fast-import" learned an option to pass these nonsense timestamps intact to allow recreating existing repositories as-is.

That could be helpful in your case.

See commit d42a2fb (30 May 2020) by Elijah Newren (newren).
^{(Merged by Junio C Hamano -- gitster -- in commit 5404183, 02 Jun 2020)}

fast-import: add new --date-format=raw-permissive format

^{Signed-off-by: Elijah Newren}

There are multiple repositories in the wild with random, invalid timezones.

Most notably is a commit from rails.git with a timezone of "+051800".

A few searches will find other repos with that same invalid timezone as well.

Further, Peff reports that GitHub relaxed their fsck checks in August 2011 to accept any timezone value, and there have been multiple reports to filter-repo about fast-import crashing while trying to import their existing repositories since they had timezone values such as "-[7349423]" and "-[43455309]".

The existing check on timezone values inside fast-import may prove useful for people who are crafting fast-import input by hand or with a new script.

For them, the check may help them avoid accidentally recording invalid dates.

(Note that this check is rather simplistic and there are still several forms of invalid dates that fast-import does not check for: dates in the future, timezone values with minutes that are not divisible by 15, and timezone values with minutes that are 60 or greater.)
While this simple check may have some value for those users, other users or tools will want to import existing repositories as-is.
Provide a --date-format=raw-permissive format that will not error out on these otherwise invalid timezones so that such existing repositories can be imported.