2 files changed, 40 insertions, 0 deletions

diff --git a/docs/python-support.md b/docs/python-support.md
index af19cd05..35806de7 100644
--- a/docs/python-support.md
+++ b/docs/python-support.md
@@ -28,5 +28,20 @@ The master branch will require Python 3.6 at a minimum.
 If the system has an older version of Python 3, then users will have to select
 the legacy Python 2 branch instead.
 
+### repo hooks
 
+Projects that use [repo hooks] run on independent schedules.
+They might migrate to Python 3 earlier or later than us.
+To support them, we'll probe the shebang of the hook script and if we find an
+interpreter in there that indicates a different version than repo is currently
+running under, we'll attempt to reexec ourselves under that.
+
+For example, a hook with a header like `#!/usr/bin/python2` will have repo
+execute `/usr/bin/python2` to execute the hook code specifically if repo is
+currently running Python 3.
+
+For more details, consult the [repo hooks] documentation.
+
+
+[repo hooks]: ./repo-hooks.md
 [repo launcher]: ../repo
diff --git a/docs/repo-hooks.md b/docs/repo-hooks.md
index e198b390..7c37c30e 100644
--- a/docs/repo-hooks.md
+++ b/docs/repo-hooks.md
@@ -83,6 +83,31 @@ then check it directly.  Hooks should not normally modify the active git repo
 the user.  Although user interaction is discouraged in the common case, it can
 be useful when deploying automatic fixes.
 
+### Shebang Handling
+
+*** note
+This is intended as a transitional feature.  Hooks are expected to eventually
+migrate to Python 3 only as Python 2 is EOL & deprecated.
+***
+
+If the hook is written against a specific version of Python (either 2 or 3),
+the script can declare that explicitly.  Repo will then attempt to execute it
+under the right version of Python regardless of the version repo itself might
+be executing under.
+
+Here are the shebangs that are recognized.
+
+* `#!/usr/bin/env python` & `#!/usr/bin/python`: The hook is compatible with
+  Python 2 & Python 3.  For maximum compatibility, these are recommended.
+* `#!/usr/bin/env python2` & `#!/usr/bin/python2`: The hook requires Python 2.
+  Version specific names like `python2.7` are also recognized.
+* `#!/usr/bin/env python3` & `#!/usr/bin/python3`: The hook requires Python 3.
+  Version specific names like `python3.6` are also recognized.
+
+If no shebang is detected, or does not match the forms above, we assume that the
+hook is compatible with both Python 2 & Python 3 as if `#!/usr/bin/python` was
+used.
+
 ## Hooks
 
 Here are all the points available for hooking.