From c00f4980660b4905e5173b4e8486eaa224f1b6d1 Mon Sep 17 00:00:00 2001
From: brandon s allbery kf8nh <allbery.b@gmail.com>
Date: Tue, 5 Nov 2024 22:40:51 -0500
Subject: [PATCH] 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        |  3 ++
 cabal-install/cabal-install.cabal             | 11 ++++++
 cabal-install/src/Distribution/Client/Main.hs |  5 ++-
 .../src/Distribution/Client/Version.hs        | 38 +++++++++++++++++++
 cabal.project                                 |  5 +++
 cabal.release.project                         |  7 ++++
 cabal.validate.project                        |  5 +++
 7 files changed, 73 insertions(+), 1 deletion(-)

diff --git a/Cabal/src/Distribution/Simple/Utils.hs b/Cabal/src/Distribution/Simple/Utils.hs
index d51601e5c27..c771b9e6764 100644
--- a/Cabal/src/Distribution/Simple/Utils.hs
+++ b/Cabal/src/Distribution/Simple/Utils.hs
@@ -9,6 +9,9 @@
 {-# LANGUAGE LambdaCase #-}
 {-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE ScopedTypeVariables #-}
+#ifdef GIT_REV
+{-# LANGUAGE TemplateHaskell #-}
+#endif
 
 -----------------------------------------------------------------------------
 
diff --git a/cabal-install/cabal-install.cabal b/cabal-install/cabal-install.cabal
index 68845e4b8b4..2aa2a6741d7 100644
--- a/cabal-install/cabal-install.cabal
+++ b/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
 
diff --git a/cabal-install/src/Distribution/Client/Main.hs b/cabal-install/src/Distribution/Client/Main.hs
index e6278a5ef9a..7582ffcf5a8 100644
--- a/cabal-install/src/Distribution/Client/Main.hs
+++ b/cabal-install/src/Distribution/Client/Main.hs
@@ -173,7 +173,8 @@ import Distribution.Client.Utils
   , relaxEncodingErrors
   )
 import Distribution.Client.Version
-  ( cabalInstallVersion
+  ( cabalInstallGitInfo
+  , cabalInstallVersion
   )
 
 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 "
diff --git a/cabal-install/src/Distribution/Client/Version.hs b/cabal-install/src/Distribution/Client/Version.hs
index f5c6bec510d..e50f4231090 100644
--- a/cabal-install/src/Distribution/Client/Version.hs
+++ b/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
diff --git a/cabal.project b/cabal.project
index e368c280c99..8443cb96d7f 100644
--- a/cabal.project
+++ b/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
diff --git a/cabal.release.project b/cabal.release.project
index a321282a95e..04517024e32 100644
--- a/cabal.release.project
+++ b/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
diff --git a/cabal.validate.project b/cabal.validate.project
index 52c78411107..5075458c1b8 100644
--- a/cabal.validate.project
+++ b/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