How to search a Git repository by commit message?

Question

I checked some source code into GIT with the commit message "Build 0051".

However, I can't seem to find that source code any more - how do I extract this source from the GIT repository, using the command line?

Update

1. Checked in versions 0043, 0044, 0045 and 0046 using SmartGIT.
2. Checked out 0043, and checked in versions up to 0051 on a different branch.
3. Checked out 0043 again.
4. Now, 0051 has disappeared.

Update

The source code is definitely there, now its a matter of checking it out:

C:\Source>git log -g --grep="0052"
commit 77b1f718d19e5cf46e2fab8405a9a0859c9c2889
Reflog: HEAD@{10} (unknown <Mike@.(none)>)
Reflog message: commit: 20110819 - 1724 - GL: Intermediate version. File version:  v0.5.0 build 0052.
Author: unknown <Mike@.(none)>
Date:   Fri Aug 19 17:24:51 2011 +0100

    20110819 - 1724 - GL: Intermediate version. File version: v0.5.0 build 0052.

C:\Source>

Answer 1

To search the commit log (across all branches) for the given text:

git log --all --grep='Build 0051'

To search the actual content of commits through a repo's history, use:

git grep 'Build 0051' $(git rev-list --all)

to show all instances of the given text, the containing file name, and the commit sha1.

Finally, as a last resort in case your commit is dangling and not connected to history at all, you can search the reflog itself with the -g flag (short for --walk-reflogs:

git log -g --grep='Build 0051'

EDIT: if you seem to have lost your history, check the reflog as your safety net. Look for Build 0051 in one of the commits listed by

git reflog

You may have simply set your HEAD to a part of history in which the 'Build 0051' commit is not visible, or you may have actually blown it away. The git-ready reflog article may be of help.

To recover your commit from the reflog: do a git checkout of the commit you found (and optionally make a new branch or tag of it for reference)

git checkout 77b1f718d19e5cf46e2fab8405a9a0859c9c2889
# alternative, using reflog (see git-ready link provided)
# git checkout HEAD@{10}
git checkout -b build_0051 # make a new branch with the build_0051 as the tip