user-manual: finding commits referencing given file content
Another amusing git exploration example brought up in irc. (Credit to
aeruder for the complete solution.)
Signed-off-by: "J. Bruce Fields" <bfields@citi.umich.edu>
diff --git a/Documentation/user-manual.txt b/Documentation/user-manual.txt
index 1ab3d4b..222171b 100644
--- a/Documentation/user-manual.txt
+++ b/Documentation/user-manual.txt
@@ -921,6 +921,22 @@
and then he just cut-and-pastes the output commands after verifying that
they look OK.
+Finding commits referencing a file with given content
+-----------------------------------------------------
+
+Somebody hands you a copy of a file, and asks which commits modified a
+file such that it contained the given content either before or after the
+commit. You can find out with this:
+
+-------------------------------------------------
+$ git log --raw -r --abbrev=40 --pretty=oneline -- filename |
+ grep -B 1 `git hash-object filename`
+-------------------------------------------------
+
+Figuring out why this works is left as an exercise to the (advanced)
+student. The gitlink:git-log[1], gitlink:git-diff-tree[1], and
+gitlink:git-hash-object[1] man pages may prove helpful.
+
[[Developing-with-git]]
Developing with git
===================
