feat: make git revision accessable to nix build

src/Handler/Info.hs

@@ -1,4 +1,4 @@
--- SPDX-FileCopyrightText: 2022 Felix Hamann <felix.hamann@campus.lmu.de>,Gregor Kleen <gregor.kleen@ifi.lmu.de>,Sarah Vaupel <sarah.vaupel@ifi.lmu.de>,Sarah Vaupel <vaupel.sarah@campus.lmu.de>,Steffen Jost <jost@tcs.ifi.lmu.de>,Winnie Ros <winnie.ros@campus.lmu.de>
+-- SPDX-FileCopyrightText: 2022-2023 Felix Hamann <felix.hamann@campus.lmu.de>, Gregor Kleen <gregor@kleen.consulting>, Sarah Vaupel <sarah.vaupel@ifi.lmu.de>, Steffen Jost <jost@tcs.ifi.lmu.de>, Winnie Ros <winnie.ros@campus.lmu.de>
 --
 -- SPDX-License-Identifier: AGPL-3.0-or-later
 
@@ -43,7 +43,7 @@ pickLegalExternalLang = do
 getVersionR :: Handler TypedContent
 getVersionR = selectRep $ do
   provideRep $
-    return ($gitDescribe :: Text)
+    return ($orGitRevisionEnv gitDescribe :: Text)
   provideRep getInfoR
 
 
@@ -99,7 +99,7 @@ getInfoR = do
         knownBugs      = $(i18nWidgetFile "knownBugs")
         implementation = $(i18nWidgetFile "implementation")
         gitInfo :: Text
-        gitInfo  = $gitDescribe <> " (" <> $gitCommitDate <> ")"
+        gitInfo  = $(orGitRevisionEnv gitDescribeDate)
     $(widgetFile "versionHistory")
 
 

src/Handler/Info/TH.hs

@@ -1,20 +1,24 @@
--- SPDX-FileCopyrightText: 2022 Gregor Kleen <gregor.kleen@ifi.lmu.de>
+-- SPDX-FileCopyrightText: 2022-2023 Gregor Kleen <gregor@kleen.consulting>
 --
 -- SPDX-License-Identifier: AGPL-3.0-or-later
 
 module Handler.Info.TH
   ( glossaryTerms
+  , orGitRevisionEnv, gitDescribeDate
   ) where
 
 import Import
 
 import Language.Haskell.TH
+import Language.Haskell.TH.Lib (stringE)
 
 import qualified Data.Char as Char
 
 import qualified Data.Map.Strict as Map
 import qualified Data.Text as Text
 
+import Development.GitRev
+
 
 glossaryTerms :: FilePath -> Q Exp
 glossaryTerms basename = do
@@ -24,3 +28,9 @@ glossaryTerms basename = do
   where
     unPathPiece :: Text -> String
     unPathPiece = repack . mconcat . map (over _head Char.toUpper) . Text.splitOn "-"
+
+orGitRevisionEnv :: Q Exp -> Q Exp
+orGitRevisionEnv cont = maybe cont stringE =<< runIO (lookupEnv "GIT_REVISION")
+
+gitDescribeDate :: Q Exp
+gitDescribeDate = [e|$gitDescribe <> " (" <> $gitCommitDate <> ")"|]