Command-line option to report version

1 files changed, 32 insertions, 0 deletions

diff --git a/src/Version/Git.hs b/src/Version/Git.hs
new file mode 100644
index 0000000..fcd54a0
--- /dev/null
+++ b/src/Version/Git.hs
@@ -0,0 +1,32 @@
+module Version.Git (
+    tGitVersion,
+) where
+
+import Language.Haskell.TH
+import Language.Haskell.TH.Syntax
+import Language.Haskell.TH.Syntax.Compat
+
+import System.Directory
+import System.Exit
+import System.Process
+
+tGitVersion :: SpliceQ (Maybe String)
+tGitVersion = unsafeSpliceCoerce $ do
+    let git args = do
+            (ExitSuccess, out, _) <- readCreateProcessWithExitCode
+                (proc "git" $ [ "--git-dir=./.git", "--work-tree=." ] ++ args) ""
+            return $ lines out
+
+    mbver <- runIO $ do
+        doesPathExist "./.git" >>= \case
+            False -> return Nothing
+            True -> do
+                desc:_ <- git [ "describe", "--always", "--dirty= (dirty)" ]
+                files <- git [ "ls-files" ]
+                return $ Just (desc, files)
+
+    case mbver of
+        Just (_, files) -> mapM_ addDependentFile files
+        Nothing -> return ()
+
+    lift (fst <$> mbver :: Maybe String)