Jonathan Bourke

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git Lost and Found

comments git, branch, fsck, --lost-found edit

I got asked a git question the other day and thought I should blog my reply.

Is it safe to run this? git branch -f master origin/master

To which I replied: Yes, with a but.

##The But? Any local commits you have maybe orphaned.

##Why? What you need to know about that command is that if (and let’s assume it does) the branch master exists, then the -f switch will mean that the local branch gets reset to the remote branch, thus removing any local commits.

See the Options section under Branching in the manual, http://git-scm.com/docs/git-branch, for more.

##Let’s see what I mean

We will work with a local repository and two branches for this example.

E:\_scratch\gitlostfound> git init
Initialized empty Git repository in E:/_scratch/gitlostfound/.git/
E:\_scratch\gitlostfound [master]> "first test" | Out-File first.txt
E:\_scratch\gitlostfound [master]> git add . ; git commit -m "First file"
[master (root-commit) b5ee354] First file
 1 file changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 first.txt
E:\_scratch\gitlostfound [master]> "second test" | Out-File second.txt
E:\_scratch\gitlostfound [master]> git add . ; git commit -m "Second file"
[master d986f3b] Second file
 1 file changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 second.txt
E:\_scratch\gitlostfound [master]> git checkout -b somebranch
Switched to a new branch 'somebranch'
E:\_scratch\gitlostfound [somebranch]> "third test" | Out-File third.txt
E:\_scratch\gitlostfound [somebranch]> git add . ; git commit -m "Third file"
[somebranch f4203be] Third file
 1 file changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 third.txt
E:\_scratch\gitlostfound [somebranch]> "fourth test" | Out-File fourth.txt
E:\_scratch\gitlostfound [somebranch]> git add . ; git commit -m "Fourth file"
[somebranch ef3ce58] Fourth file
 1 file changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 fourth.txt
E:\_scratch\gitlostfound [somebranch]> git checkout master
Switched to branch 'master'
E:\_scratch\gitlostfound [master]> "fifth test" | Out-File fifth.txt
E:\_scratch\gitlostfound [master]> git add . ; git commit -m "Fifth file"
[master 693e3b1] Fifth file
 1 file changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 fifth.txt
E:\_scratch\gitlostfound [master]> git log --graph --abbrev-commit --decorate --format=format:'%C(bold normal)%h%C(reset) - %C(bold cyan)%aD%C(reset) %C(bold green)(%ar)%C(reset)%C(bold yellow)%d%C(reset)%n'' %C(white)%s%C(reset) %C(dim white)- %an%C(reset)' --all
* 693e3b1 - Fri, 9 May 2014 10:23:52 +1000 (65 seconds ago) (HEAD, master)
| ' Fifth file - Jonathan Bourke
| * ef3ce58 - Fri, 9 May 2014 10:23:09 +1000 (2 minutes ago) (somebranch)
| | ' Fourth file - Jonathan Bourke
| * f4203be - Fri, 9 May 2014 10:22:52 +1000 (2 minutes ago)
|/  ' Third file - Jonathan Bourke
* d986f3b - Fri, 9 May 2014 10:21:02 +1000 (4 minutes ago)
| ' Second file - Jonathan Bourke
* b5ee354 - Fri, 9 May 2014 10:19:40 +1000 (5 minutes ago)
  ' First file - Jonathan Bourke
E:\_scratch\gitlostfound [master]>

So after all that what we have is a repository with two branches. Now if we run the branch reset command that was mentioned at this start of this post an interesting thing occurs. Let’s take a look…

E:\_scratch\gitlostfound [master]> git branch -f somebranch master
E:\_scratch\gitlostfound [master]> git log --graph --abbrev-commit --decorate --format=format:'%C(bold normal)%h%C(reset) - %C(bold cyan)%aD%C(reset) %C(bold green)(%ar)%C(reset)%C(bold yellow)%d%C(reset)%n'' %C(white)%s%C(reset) %C(dim white)- %an%C(reset)' --all
* 693e3b1 - Fri, 9 May 2014 10:23:52 +1000 (4 minutes ago) (HEAD, somebranch, master)
| ' Fifth file - Jonathan Bourke
* d986f3b - Fri, 9 May 2014 10:21:02 +1000 (7 minutes ago)
| ' Second file - Jonathan Bourke
* b5ee354 - Fri, 9 May 2014 10:19:40 +1000 (8 minutes ago)
  ' First file - Jonathan Bourke
E:\_scratch\gitlostfound [master]>

Where’d the work on somebranch go?

##How do you get them back?

First we need to switch back to somebranch. This is very important because if we perform the next steps in master then the history will show that the work was originally done there and not in somebranch.

E:\_scratch\gitlostfound [master]> git checkout somebranch
Switched to branch 'somebranch'
E:\_scratch\gitlostfound [somebranch]> git fsck --lost-found
Checking object directories: 100% (256/256), done.
dangling commit ef3ce583d09f7b438c06da450f33620043cd2ce6
E:\_scratch\gitlostfound [somebranch]>

Once you ascertain which commits to reapply, simply merge that commit:

E:\_scratch\gitlostfound [somebranch]> git merge ef3ce58
Merge made by the 'recursive' strategy.
 fourth.txt | Bin 0 -> 28 bytes
 third.txt  | Bin 0 -> 26 bytes
 2 files changed, 0 insertions(+), 0 deletions(-)
 create mode 100644 fourth.txt
 create mode 100644 third.txt
E:\_scratch\gitlostfound [somebranch]> git log --graph --abbrev-commit --decorate --format=format:'%C(bold normal)%h%C(reset) - %C(bold cyan)%aD%C(reset) %C(bold green)(%ar)%C(reset)%C(bold yellow)%d%C(reset)%n'' %C(white)%s%C(reset) %C(dim white)- %an%C(reset)' --all
*   9e45311 - Fri, 9 May 2014 10:29:19 +1000 (5 seconds ago) (HEAD, somebranch)
|\  ' Merge commit 'ef3ce58' - Jonathan Bourke
| * ef3ce58 - Fri, 9 May 2014 10:23:09 +1000 (6 minutes ago)
| | ' Fourth file - Jonathan Bourke
| * f4203be - Fri, 9 May 2014 10:22:52 +1000 (7 minutes ago)
| | ' Third file - Jonathan Bourke
* | 693e3b1 - Fri, 9 May 2014 10:23:52 +1000 (6 minutes ago) (master)
|/  ' Fifth file - Jonathan Bourke
* d986f3b - Fri, 9 May 2014 10:21:02 +1000 (8 minutes ago)
| ' Second file - Jonathan Bourke
* b5ee354 - Fri, 9 May 2014 10:19:40 +1000 (10 minutes ago)
  ' First file - Jonathan Bourke
E:\_scratch\gitlostfound [somebranch]>

Done! Of course this is a very simply example, your mileage may vary.

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