multiple -m

sync, assist, import: Allow -m option to be specified multiple times, to
provide additional paragraphs for the commit message.

The option parser didn't allow multiple -m before, so there is no risk of
behavior change breaking something that was for some reason using multiple
-m already.

Pass through to git commands, so that the method used to assemble the
paragrahs is whatever git does. Which might conceivably change in the
future.

Note that git commit-tree has supported -m since git 1.7.7. commitTree
was probably not using it since it predates that version. Since the
configure script prevents building git-annex with git older than 2.1,
there is no risk that it's not supported now.

Sponsored-by: Nicholas Golder-Manning on Patreon

Annex/Import.hs

@@ -86,7 +86,7 @@ data ImportCommitConfig = ImportCommitConfig
 	{ importCommitTracking :: Maybe Sha
 	-- ^ Current commit on the remote tracking branch.
 	, importCommitMode :: Git.Branch.CommitMode
-	, importCommitMessage :: String
+	, importCommitMessages :: [String]
 	}
 
 {- Buils a commit for an import from a special remote.
@@ -251,7 +251,7 @@ buildImportCommit' remote importcommitconfig mtrackingcommit imported@(History t
 
 	mkcommit parents tree = inRepo $ Git.Branch.commitTree
 		(importCommitMode importcommitconfig)
-		(importCommitMessage importcommitconfig)
+		(importCommitMessages importcommitconfig)
 		parents
 		tree