Yet another "how to rebase one Git repo onto another" issue

Question

I have a similar problem as the one in this question, but with a fundamental difference:

We got the code from a client, for evaluation and start working before signing contracts. They gave us pure code, no git repo. We created a git repo from it and used it for some time.

As the project got the go-ahead, we got access to their git repo for that project. That code has evolved as well. I am supposed to create a new branch on their repo and rebase our work into that new branch.

Reading the aforementioned question, I learned about graft, where a repo B can have a parent repo A by using graft to tell that the base of B is some commit of A. But in my case, I don't know which commit of A (their repo) is the base of B (my repo).

It's a very odd situation, where two repos can be considered different - since I don't know the commit that could be the parent of the second, but the changes in the second should be rebased to the files in the first.

How about you ask the client which revision they sent you? – Chronial Dec 22 '13 at 17:32 — Chronial, Dec 22 '13 at 17:32
I wish life was so simple :) – Roberto Dec 23 '13 at 02:39 — Roberto, Dec 23 '13 at 02:39

jthill · Accepted Answer · 2013-12-22T23:37:32.113

2

Interpreting your question as "find the revision(s) in their repository with the tree for the source they sent you",

ours=$( git rev-parse our_commit_of_their_source^{tree} )
git rev-list --pretty=format:'%h %T %s' | grep $ours

If there aren't any identical trees, you can at least efficiently list the files with differences with git diff-tree --name-status $ours $theirs to see how many files in a commit are different than yours, it's one way to do what Robin suggested. Maybe do the diff-trees with '-b` to ignore whitespace-only changes.

edited Dec 22 '13 at 23:37

answered Dec 22 '13 at 16:07

jthill

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What if we have a slightly different set o files when we started our repo? Someone may changed .gitignore or added a few files. Unfortunately I'm using Windows and MINGW32 crashes when I run the first command, I think the output is just too big set to `ours`. – Roberto Dec 22 '13 at 20:50
my apologies, `show` should have been a simple `rev-parse`. Fixed that. – jthill Dec 22 '13 at 23:19
@Roberto for the we-changed-something-first scenario, best I can do is some ideas for how to help with the judicious selection of what to manually compare in Robin's answer – jthill Dec 22 '13 at 23:41

score 1 · Answer 2 · answered Dec 22 '13 at 12:30

You can maybe do a search over all the revisions in some reasonable date range, to find the matching revision in their repo. Of course you will have to ignore files in .gitignore.

But a reasonable first guess is that the revision will be on the same day as the day they sent you the code... so you should only have to check a few revisions.

You can use git diff HEAD to check for differences.

Yet another "how to rebase one Git repo onto another" issue

2 Answers2