[PATCH 0 of 2] keyword extension: implementation without pretxncommit hook

[Christian Ebert]

Hello,

Another stab at keyword expansion.

This version does not rely on a pretxncommit hook to
expand keywords in the working directory after a commit.

The former might break once issue273 is solved.
Instead it wraps commit and updates dirstate "openly"
after overwriting the committed (and explicitly configured)
text files.

Also it tries hard to avoid to be loaded unnecessarily.

c