add compiler info to --version

I'm not sure if this counts as a significant change or not, since
it's possible scripts depend on the output. (The git info change
doesn't really count, since it's only operable on unreleased
versions.)

Author: geekosaur

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

@@ -172,6 +172,7 @@ import Distribution.Client.Utils
 import Distribution.Client.Version
   ( cabalInstallGitInfo
   , cabalInstallVersion
+  , cabalInstallCompilerInfo
   )
 
 import Distribution.Package (packageId)
@@ -424,6 +425,8 @@ mainWorker args = do
           ++ display cabalVersion
           ++ " of the Cabal library "
           ++ cabalGitInfo'
+          ++ "\nwith "
+          ++ cabalInstallCompilerInfo
       where
         cabalGitInfo'
           | cabalGitInfo == cabalInstallGitInfo = "(in-tree)"

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

@@ -7,8 +7,12 @@
 module Distribution.Client.Version
   ( cabalInstallVersion
   , cabalInstallGitInfo
+  , cabalInstallCompilerInfo
   ) where
 
+import Data.List (intercalate)
+import qualified Data.Version as DV
+import qualified System.Info as SI
 import Distribution.Version
 
 import qualified Paths_cabal_install as PackageInfo
@@ -28,9 +32,27 @@ import GitHash
 cabalInstallVersion :: Version
 cabalInstallVersion = mkVersion' PackageInfo.version
 
+-- |
+-- `cabal-install` compiler information.
+cabalInstallCompilerInfo :: String
+cabalInstallCompilerInfo = let ci =
+#if MIN_VERSION_base(4,15,0)
+                                    SI.fullCompilerVersion
+#else
+                                    SI.compilerVersion
+#endif
+                              in concat [ SI.compilerName
+                                        , " "
+                                        , intercalate "." (map show (DV.versionBranch ci))
+                                        , " on "
+                                        , SI.os
+                                        , " "
+                                        , SI.arch
+                                        ]
+
 -- |
 -- `cabal-install` Git information. Only filled in if built in a Git tree in
--- developmnent mode and Template Haskell is available.
+-- development mode and Template Haskell is available.
 cabalInstallGitInfo :: String
 #ifdef GIT_REV
 cabalInstallGitInfo = if giHash' == ""