Add Ignore Changes To A Tracked File as a git til.

README.md

@@ -32,6 +32,7 @@ smart people at [Hashrocket](http://hashrocket.com/).
 - [Clean Out All Local Branches](git/clean-out-all-local-branches.md)
 - [Delete All Untracked Files](git/delete-all-untracked-files.md)
 - [Dry Runs in Git](git/dry-runs-in-git.md)
+- [Ignore Changes To A Tracked File](git/ignore-changes-to-a-tracked-file.md)
 - [Intent To Add](git/intent-to-add.md)
 - [Last Commit A File Appeared In](git/last-commit-a-file-appeared-in.md)
 - [List Filenames Without The Diffs](git/list-filenames-without-the-diffs.md)

git/ignore-changes-to-a-tracked-file.md

@@ -0,0 +1,14 @@
+# Ignore Changes To A Tracked File
+
+Files that should never be tracked are listed in your `.gitignore` file. But
+what about if you want to ignore some local changes to a tracked file?
+
+You can tell git to assume the file is unchanged
+
+```bash
+$ git update-index --assume-unchanged <some-file>
+```
+
+Reversing the process can be done with the `--no-assume-unchanged` flag.
+
+[source](http://blog.pagebakers.nl/2009/01/29/git-ignoring-changes-in-tracked-files/)