Document how to ignore specific files in a diff (#1668)

Author: jyn514

Diff for: src/git.md

@@ -508,6 +508,18 @@ See [the docs for `--color-moved`](https://git-scm.com/docs/git-diff#Documentati
 See [the relevant section for PR authors](#git-range-diff). This can be useful for comparing code
 that was force-pushed to make sure there are no unexpected changes.
 
+### Ignoring changes to specific files
+
+Many large files in the repo are autogenerated. To view a diff that ignores changes to those files,
+you can use the following syntax (e.g. Cargo.lock):
+
+```
+git log -p ':!Cargo.lock'
+```
+
+Arbitrary patterns are supported (e.g. `:!compiler/*`). Patterns use the same syntax as
+`.gitignore`, with `:` prepended to indicate a pattern.
+
 ## Git submodules
 
 **NOTE**: submodules are a nice thing to know about, but it *isn't* an absolute