Wsrtjtyk

How can I convert an already cloned git repository to a shallow repository?

The git repository is downloaded through a script outside of my control so I cannot do a shallow clone.

The reason for doing this is to save disk space. (Yes, I'm really short on disk space so even though a shallow repository doesn't save much, it is needed.)

I already tried

git repack -a -d -f -depth=1

But that actually made the repository larger.

Let's say the earliest commit you want to keep has a SHA1 of c0ffee.

1. Create a new empty branch


2. Checkout the tree of the earliest commit you want to keep, without actually checking out the commit: git checkout c0ffee -- . (Now HEAD is still pointing to your new empty branch, but your working tree and index both look like the tree of c0ffee)


3. Commit the whole tree: git commit -m "Initial commit, copied from c0ffee"
   


4. At this point git diff-tree newbranch c0ffee should produce no output -- they have the same tree. (Alternatively, you could do git show -s c0ffee --format=%T and git show -s newbranch --format=%T and they should show the same hash.)


5. git rebase --onto newbranch c0ffee master


6. git branch -d newbranch


7. git gc

This worked for me:

git pull --depth 1

git gc --prune=all

You can convert git repo to a shallow one in place along this lines:

git show-ref -s HEAD > .git/shallow

git reflog expire --expire=0

git prune

git prune-packed

Make sure to make backup since this is destructive operation, also keep in mind that cloning nor fetching from shallow repo is not supported! To really remove all the history you also need to remove all references to previous commits before pruning.

Solution:

git clone --depth 1 file:///full/path/to/original/dir destination

Note that the first "address" should be a file://, that's important. Also, git will assume your original local file:// address to be the "remote" ("origin"), so you'll need to update the new repository specifying the correct git remote.

Note that a shallow repo (like one with git clone --depth 1 as a way to convert an existing repo to a shallow one) can fail on git repack.

See commit 5dcfbf5, commit 2588f6e, commit 328a435 (24 Oct 2018) by Johannes Schindelin (dscho).
^{(Merged by Junio C Hamano -- gitster -- in commit ea100b6, 06 Nov 2018)}

repack -ad: prune the list of shallow commits

git repack can drop unreachable commits without further warning,
making the corresponding entries in .git/shallow invalid, which causes
serious problems when deepening the branches.

One scenario where unreachable commits are dropped by git repack is
when a git fetch --prune (or even a git fetch when a ref was
force-pushed in the meantime) can make a commit unreachable that was
reachable before.

Therefore it is not safe to assume that a git repack -adlf will keep unreachable commits alone (under the assumption that they had not been packed in the first place, which is an assumption at least some of Git's code seems to make).

This is particularly important to keep in mind when looking at the
.git/shallow file: if any commits listed in that file become
unreachable, it is not a problem, but if they go missing, it is a
problem.

One symptom of this problem is that a deepening fetch may now
fail with:

fatal: error in object: unshallow <commit-hash>

To avoid this problem, let's prune the shallow list in git repack when the -d option is passed, unless -A is passed, too (which would force the now-unreachable objects to be turned into loose objects instead of being deleted).

Additionally, we also need to take --keep-reachable and --unpack-unreachable=<date> into account.

Note: an alternative solution discussed during the review of this patch
was to teach git fetch to simply ignore entries in .git/shallow if the
corresponding commits do not exist locally.

A quick test, however, revealed that the .git/shallow file is written during a shallow clone, in which case the commits do not exist, either, but the "shallow" line
does need to be sent.

Therefore, this approach would be a lot more finicky than the approach presented by the this patch.