.git: fetch and apply commits of removed branch

Question

I have some old changes I made, committed and pushed to remote (bitbucket) repo. These changes was not merged to any other branch. Branch itself was removed locally and from remote repo.

But, as I can see in bitbucket web, commits included to removed branch still there (in repo). I googled a lot, but did not find a way, how to retrieve commits of removed branch from remote. The only I can do is to see them in bitbucket web and get sha of commit there.

I saw some examples like

git checkout <sha>

or

git checkout -b <branch-name> <sha>

But always get the following error

fatal: reference is not a tree: <sha>

So, is it possible and how I can retrieve (fetch) these commits from remote, crate branch from them, merge to release branch?

UPD:

To be more specific, I have created a repo, new branch, make a commit in this ne branch and remove branch:

Repo https://github.com/yurybond/stackowerflow-rocks

Link to (standalone) commit from removed branch https://github.com/yurybond/stackowerflow-rocks/commit/a1c1540abd453773b3ce6445d01e51ad336bbe84

The question is still the same: How to retreive commit (a1c1540abd453773b3ce6445d01e51ad336bbe84) that belongs to removed branch?

Answer 1

You can manually download missing commits in mbox format and apply them manually with git am. For example:

• github (repository you linked to):

    $ wget https://github.com/yurybond/stackowerflow-rocks/commit/a1c1540abd453773b3ce6445d01e51ad336bbe84.patch && git am a1c1540abd453773b3ce6445d01e51ad336bbe84.patch
  

• gitlab:

    $ wget https://git.weboob.org/weboob/devel/commit/bba7e1b8ffb0743b57f202cf9cdb43fda209fa43.patch && git am bba7e1b8ffb0743b57f202cf9cdb43fda209fa43.patch
  

• bitbucket:

    $ wget https://bitbucket.org/Kasreyn/linux-3-9-rc3-moxart/commits/434e8f69db2c3effdc8741139adb722a68dfcccd/raw -O 434e8f69db2c3effdc8741139adb722a68dfcccd.patch && git am 434e8f69db2c3effdc8741139adb722a68dfcccd.patch
  

Notice that git am will not only apply textual patch but will also recreate a whole commit on the current branch.

If you removed a branch from the remote repository there is no way to get it back from the remote reposityr. However, normally you still might be able to restore a removed branch locally thanks to git reflog. See the following example.

First, create a new non-bare repository:

$ git init
Initialized empty Git repository in /tmp/reflog-test/.git/

Add file and create a new commit on master branch:

$ touch file
$ git add .
$ git commit -m 'Initial commit'
[master (root-commit) 81fc76d] Initial commit
 1 file changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 file

Switch to a new branch creatively named new-branch:

$ git checkout -b new-branch
Switched to a new branch 'new-branch'

Modify file and commit changes:

$ echo new-branch >> file
$ git commit -am 'commit on new-branch'
[new-branch 9c457c6] commit on new-branch
 1 file changed, 1 insertion(+)

Switch back to master:

$ git checkout -
Switched to branch 'master'
$ git branch
* master
  new-branch

Remove new-branch

$ git branch -D new-branch
Deleted branch new-branch (was 9c457c6).

It's gone:

$ git branch
* master
$ git log new-branch
fatal: ambiguous argument 'new-branch': unknown revision or path not in the working tree.
Use '--' to separate paths from revisions, like this:
'git <command> [<revision>...] -- [<file>...]'

However, you should still be able to reference the commit:

$ git show --stat 9c457c6
commit 9c457c69de8a54376a2614ca8cfc0f515c64676c
Author: Arkadiusz Drabczyk <[email protected]>
Date:   Tue Apr 3 10:43:49 2018 +0200

commit on new-branch

 file | 1 +
 1 file changed, 1 insertion(+)

Even though it can't be found on any branch. The following command returns nothing:

$ git branch --contains  9c457c6

Reflog shows all actions one did in a repository:

$ git reflog
dbc721a HEAD@{0}: checkout: moving from new-branch to master
9c457c6 HEAD@{1}: commit: commit on new-branch
dbc721a HEAD@{2}: checkout: moving from master to new-branch
dbc721a HEAD@{3}: commit (initial): Initial commit

As you see it also has 9c457c6 commit we did on the new-branch. Only when reflog is expired and garbage collector is run 9c457c6 becomes unreachable:

$ git reflog expire --expire=all  --all
$ git gc --prune=now
Counting objects: 3, done.
Writing objects: 100% (3/3), done.
Total 3 (delta 0), reused 0 (delta 0)
$ git show 9c457c6
fatal: ambiguous argument '9c457c6': unknown revision or path not in the working tree.
Use '--' to separate paths from revisions, like this:
'git <command> [<revision>...] -- [<file>...]'

By default reflog entries expire after 90 days and git gc is run automatically after some commands so if you have removed the branch relatively recently you should be able to restore it.