How to search a Git repository by commit message?

I put this in my ~/.gitconfig:

[alias]
    find = log --pretty=\"format:%Cgreen%H %Cblue%s\" --name-status --grep

Then I can type "git find string" and I get a list of all the commits containing that string in the message. For example, to find all commits referencing ticket #33:

029a641667d6d92e16deccae7ebdeef792d8336b Added isAttachmentEditable() and isAttachmentViewable() methods. (references #33)
M       library/Dbs/Db/Row/Login.php

a1bccdcd29ed29573d2fb799e2a564b5419af2e2 Add permissions checks for attachments of custom strategies. (references #33).
M       application/controllers/AttachmentController.php

38c8db557e5ec0963a7292aef0220ad1088f518d Fix permissions. (references #33)
M       application/views/scripts/attachment/_row.phtml

041db110859e7259caeffd3fed7a3d7b18a3d564 Fix permissions. (references #33)
M       application/views/scripts/attachment/index.phtml

388df3b4faae50f8a8d8beb85750dd0aa67736ed Added getStrategy() method. (references #33)
M       library/Dbs/Db/Row/Attachment.php

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

Though a bit late, there is :/ which is the dedicated notation to specify a commit (or revision) based on the commit message, just prefix the search string with :/, e.g.:

git show :/keyword(s)

Here <keywords> can be a single word, or a complex regex pattern consisting of whitespaces, so please make sure to quote/escape when necessary, e.g.:

git log -1 -p ":/a few words"

Alternatively, a start point can be specified, to find the closest commit reachable from a specific point, e.g.:

git show 'HEAD^{/fix nasty bug}'

See: git revisions manual.

git log --grep="Build 0051"

should do the trick