added hooks corresponding to annex.*-command

* Added freezecontent-annex and thawcontent-annex hooks that
  correspond to the git configs annex.freezecontent and
  annex.thawcontent.
* Added secure-erase-annex hook that corresponds to the git config
  annex.secure-erase-command.
* Added commitmessage-annex hook that corresponds to the git config
  annex.commitmessage-command.
* Added http-headers-annex hook that corresponds to the git config
  annex.http-headers-command.
  that correspond to the post-update-annex and pre-commit-annex hooks.

The use case for these is eg, setting up a git repository that is run in a
container, where the easiest way to provide a script is by putting it in
.git/hooks/, rather than copying it into the container in a way that puts
it in PATH.

This is all the ones that make sense to add for annex.*-config git configs.
annex.youtube-dl-command is not a hook, it's telling git-annex what command
to run. So is annex.shared-sop-command. So omitted those.

May later also want to add hooks corresponding to
`remote.<name>.annex-cost-command` etc.

Sponsored-by: the NIH-funded NICEMAN (ReproNim TR&D3) project

Annex/Perms.hs

@@ -33,6 +33,7 @@ module Annex.Perms (
 ) where
 
 import Annex.Common
+import Annex.Hook
 import Utility.FileMode
 import Git
 import Git.ConfigTypes
@@ -340,24 +341,24 @@ modifyContentDirWhenExists f a = do
 	either throwM return v
 
 hasFreezeHook :: Annex Bool
-hasFreezeHook = isJust . annexFreezeContentCommand <$> Annex.getGitConfig
+hasFreezeHook = 
+	(isJust . annexFreezeContentCommand <$> Annex.getGitConfig)
+		<||>
+	(doesAnnexHookExist freezeContentAnnexHook)
 
 hasThawHook :: Annex Bool
-hasThawHook = isJust . annexThawContentCommand <$> Annex.getGitConfig
+hasThawHook =
+	(isJust . annexThawContentCommand <$> Annex.getGitConfig)
+		<||>
+	(doesAnnexHookExist thawContentAnnexHook)
 
 freezeHook :: RawFilePath -> Annex ()
-freezeHook p = maybe noop go =<< annexFreezeContentCommand <$> Annex.getGitConfig
-  where
-	go basecmd = void $ liftIO $
-		boolSystem "sh" [Param "-c", Param $ gencmd basecmd]
-	gencmd = massReplace [ ("%path", shellEscape (fromRawFilePath p)) ]
+freezeHook = void . runAnnexPathHook "%path"
+	freezeContentAnnexHook annexFreezeContentCommand
 
 thawHook :: RawFilePath -> Annex ()
-thawHook p = maybe noop go =<< annexThawContentCommand <$> Annex.getGitConfig
-  where
-	go basecmd = void $ liftIO $
-		boolSystem "sh" [Param "-c", Param $ gencmd basecmd]
-	gencmd = massReplace [ ("%path", shellEscape (fromRawFilePath p)) ]
+thawHook = void . runAnnexPathHook "%path"
+	thawContentAnnexHook annexThawContentCommand
 
 {- Calculate mode to use for a directory from the mode to use for a file.
  -