record Git revision in devel builds

`cabal --version` in such builds will include the Git commit and
branch (if not `master`).

Cabal/src/Distribution/Simple/Utils.hs

@@ -9,6 +9,9 @@
 {-# LANGUAGE LambdaCase #-}
 {-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE ScopedTypeVariables #-}
+#ifdef GIT_REV
+{-# LANGUAGE TemplateHaskell #-}
+#endif
 
 -----------------------------------------------------------------------------
 

cabal-install/cabal-install.cabal

@@ -39,6 +39,11 @@ Flag lukko
   default:      True
   manual:       True
 
+flag git-rev
+  description: include Git revision hash in version
+  default: False
+  manual: True
+
 common warnings
     ghc-options:
       -Wall
@@ -269,6 +274,9 @@ library
     if impl(ghc >=8.2)
       build-depends: process >= 1.6.15.0
 
+    if flag(git-rev)
+      build-depends: githash ^>= 0.1.7.0
+      cpp-options: -DGIT_REV
 
 executable cabal
     import: warnings, base-dep
@@ -282,6 +290,9 @@ executable cabal
     if os(aix)
         extra-libraries: bsd
 
+    if flag(git-rev)
+      ghc-options: -DGIT_REV
+
     build-depends:
         cabal-install
 

cabal-install/src/Distribution/Client/Main.hs

@@ -174,6 +174,7 @@ import Distribution.Client.Utils
   )
 import Distribution.Client.Version
   ( cabalInstallVersion
+  , cabalInstallGitInfo
   )
 
 import Distribution.Package (packageId)
@@ -413,6 +414,8 @@ mainWorker args = do
       putStrLn $
         "cabal-install version "
           ++ display cabalInstallVersion
+          ++ " "
+          ++ cabalInstallGitInfo
           ++ "\ncompiled using version "
           ++ display cabalVersion
           ++ " of the Cabal library "

cabal-install/src/Distribution/Client/Version.hs

@@ -1,13 +1,51 @@
+{-# LANGUAGE CPP #-}
+#ifdef GIT_REV
+{-# LANGUAGE TemplateHaskell #-}
+#endif
+
 -- | Provides the version number of @cabal-install@.
 module Distribution.Client.Version
   ( cabalInstallVersion
+  , cabalInstallGitInfo
   ) where
 
 import Distribution.Version
 
 import qualified Paths_cabal_install as PackageInfo
 
+#ifdef GIT_REV
+import Data.Either (isLeft)
+import GitHash
+  ( giHash
+  , giBranch
+  , giCommitDate
+  , tGitInfoCwdTry
+  )
+#endif
+
 -- |
 -- This value determines the output of `cabal-install --version`.
 cabalInstallVersion :: Version
 cabalInstallVersion = mkVersion' PackageInfo.version
+
+-- |
+-- `cabal-install` Git information. Only filled in if built in a Git tree in
+-- developmnent mode and Template Haskell is available.
+cabalInstallGitInfo :: String
+#ifdef GIT_REV
+cabalInstallGitInfo = concat [ "(commit "
+                             , giHash'
+                             , branchInfo
+                             , ", "
+                             , either (const "") giCommitDate gi'
+                             , ")"
+                             ]
+  where
+    gi' = $$tGitInfoCwdTry
+    giHash' = take 7 . either (const "") giHash $ gi'
+    branchInfo | isLeft gi' = ""
+               | either id giBranch gi' == "master" = ""
+               | otherwise = " on " <> either id giBranch gi'
+#else
+cabalInstallGitInfo = ""
+#endif

cabal.project

@@ -4,3 +4,8 @@ import: project-cabal/pkgs.config
 import: project-cabal/constraints.config
 
 tests: True
+
+-- if you are developing on a system without TH, use a `cabal.project.local`
+-- to disable this
+package cabal-install
+  flags: +git-rev

cabal.release.project

@@ -3,3 +3,10 @@ import: project-cabal/pkgs/install.config
 import: project-cabal/pkgs/tests.config
 
 index-state: hackage.haskell.org 2024-09-06T14:16:40Z
+
+-- never include this or its TH dependency in a release!
+package Cabal
+  flags: -git-rev
+
+package cabal-install
+  flags: -git-rev

cabal.validate.project

@@ -7,3 +7,8 @@ tests: True
 write-ghc-environment-files: never
 program-options
   ghc-options: -Werror
+
+-- if you are developing on a system without TH, use a `cabal.validate.project.local`
+-- to disable this
+package cabal-install
+  flags: +git-rev