[Searched words]
filter a git log
filter log output command line
grep git history
git view commit
git re-apply commit

To do a simple search through Git's commit messages (another reason to write useful information when committing!) *and* the accompanying diffs, you can use to search for dgd7.org:

git log -Sdgd7.org

Shows us, as one of a few matches:

commit 89bec60d085839fff22fdd4e387063717282edc6
Author: Benjamin
Date: Tue Jun 15 19:47:23 2010 -0400

.htaccess for live site with redirects of all aliased domain names.

To view the changes made (diff), we only need the first characters of the commit hash:
git show 89bec60

It's the right one:

commit 89bec60d085839fff22fdd4e387063717282edc6
Author: Benjamin
Date: Tue Jun 15 19:47:23 2010 -0400

.htaccess for live site with redirects of all aliased domain names.

diff --git a/drupal/.htaccess b/drupal/.htaccess
index e673753..60d5c26 100644
--- a/drupal/.htaccess
+++ b/drupal/.htaccess
@@ -62,6 +62,9 @@ DirectoryIndex index.php index.html index.htm

RewriteEngine on

+ RewriteCond %{HTTP_HOST} ^(www\.|)(definitivedrupal.com|dgd7.com|dgd7.org|dgd
+ RewriteRule ^(.*)$ http://definitivedrupal.org/$1 [L,R=301]
+
# Block access to "hidden" directories whose names begin with a period. This
# includes directories used by version control systems such as Subversion or
# Git to store control files. Files whose names begin with a period, as well

To reapply this commit automatically, we use Git's cherry-pick command, which applies it as a patch and immediately commits it with the same commit message):
git cherry-pick 89bec60

And we're done!