Re: [PATCH] post-checkout hook, and related docs and tests

"root" [off-list ref] writes:

+post-checkout
+-----------
+
+This hook is invoked when a `git-checkout` is run on a local repository.
+The hook is given two parameters: the ref of the previous HEAD, and the ref of 
+the new HEAD.  This hook cannot affect the outcome of `git-checkout`.
+
+This hook can be used to perform repository validity checks, auto-display
+differences from the previous HEAD, or set working dir metadata properties.
+

People may wonder why this is not run when they do "git checkout
otherbranch path.c"; the second sentence from the above
description implies why it shouldn't, but the first sentence
probably should state it more clearly.

What's the _semantics_ you are trying to achieve?

Why does the hook run every time git-bisect suggests the next
revision to try?

Why does the hook run when rebase starts its work?

When "git pull" or "git merge" results in a fast forward, the
situation is no different from checking out a new revision.  Why
doesn't the hook run in these cases?