adjusted branches need git 2.2.0 or newer

When git-annex is used with a git version older than 2.2.0, disable support for
adjusted branches, since GIT_COMMON_DIR is needed to update them and was first
added in that version of git.

2 files changed, 20 insertions, 1 deletions

diff --git a/Annex/AdjustedBranch.hs b/Annex/AdjustedBranch.hs
index e9e6ab461..26a24d8e6 100644
--- a/Annex/AdjustedBranch.hs
+++ b/Annex/AdjustedBranch.hs
@@ -21,6 +21,8 @@ module Annex.AdjustedBranch (
 	updateAdjustedBranch,
 	propigateAdjustedCommits,
 	checkAdjustedClone,
+	isGitVersionSupported,
+	checkVersionSupported,
 ) where
 
 import Annex.Common
@@ -39,6 +41,8 @@ import Git.Env
 import Git.Index
 import Git.FilePath
 import qualified Git.LockFile
+import qualified Git.Version
+import Annex.Version
 import Annex.CatFile
 import Annex.Link
 import Annex.AutoMerge
@@ -507,3 +511,15 @@ checkAdjustedClone = go =<< inRepo Git.Branch.current
 				setBasisBranch basis remotebranch
 			unlessM (inRepo $ Git.Ref.exists origbranch) $
 				inRepo $ Git.Branch.update' origbranch remotebranch
+
+-- git 2.2.0 needed for GIT_COMMON_DIR which is needed
+-- by updateAdjustedBranch to use withWorkTreeRelated.
+isGitVersionSupported :: IO Bool
+isGitVersionSupported = not <$> Git.Version.older "2.2.0"
+
+checkVersionSupported :: Annex ()
+checkVersionSupported = do
+	unlessM versionSupportsAdjustedBranch $
+		error "Adjusted branches are only supported in v6 or newer repositories."
+	unlessM (liftIO isGitVersionSupported) $
+		error "Your version of git is too old; upgrade it to 2.2.0 or newer to use adjusted branches."
diff --git a/Annex/GitOverlay.hs b/Annex/GitOverlay.hs
index 7e18d225b..e33d8a83c 100644
--- a/Annex/GitOverlay.hs
+++ b/Annex/GitOverlay.hs
@@ -40,7 +40,10 @@ withWorkTree d = withAltRepo
  - files that are related to the work tree coming from an overlay
  - directory other than the usual. This is done by pointing
  - GIT_COMMON_DIR at the regular git directory, and GIT_DIR at the
- - overlay directory. -}
+ - overlay directory.
+ -
+ - Needs git 2.2.0 or newer.
+ -}
 withWorkTreeRelated :: FilePath -> Annex a -> Annex a
 withWorkTreeRelated d = withAltRepo modrepo unmodrepo
   where