Show version with --version

README.md

@@ -223,6 +223,7 @@ Usage: niv [-s|--sources-file FILE] COMMAND
 Available options:
   -s,--sources-file FILE   Use FILE instead of nix/sources.json
   -h,--help                Show this help text
+  --version                Print version
 
 Available commands:
   init                     Initialize a Nix project. Existing files won't be

default.nix

@@ -153,9 +153,7 @@ let
     packages = ps: [ ps.niv ];
     shellHook = ''
       repl_for() {
-        haskell_version=$(cat ./package.yaml \
-          | grep -oP 'version: \K\d+.\d+.\d+' \
-          | sed 's/\./,/g' )
+        haskell_version=$(jq <./package.yaml -cMr '.version' | sed 's/\./,/g')
 
         paths_niv=$(mktemp -d)/Paths_niv.hs
 

src/Niv/Cli.hs

@@ -61,7 +61,7 @@ cli = do
       Opts.Failure $
         Opts.parserFailure pprefs pinfo Opts.ShowHelpText mempty
     execParserPure' pprefs pinfo args = Opts.execParserPure pprefs pinfo args
-    opts = Opts.info ((,) <$> parseFindSourcesJson <*> (parseCommand <**> Opts.helper)) $ mconcat desc
+    opts = Opts.info ((,) <$> parseFindSourcesJson <*> (parseCommand <**> Opts.helper <**> versionflag)) $ mconcat desc
     desc =
       [ Opts.fullDesc,
         Opts.headerDoc $ Just $
@@ -78,6 +78,11 @@ cli = do
               <> Opts.help "Use FILE instead of nix/sources.json"
           )
         <|> pure Auto
+    versionflag :: Opts.Parser (a -> a)
+    versionflag =
+      Opts.abortOption (Opts.InfoMsg (showVersion version)) $
+        mconcat
+          [Opts.long "version", Opts.hidden, Opts.help "Print version"]
 
 parseCommand :: Opts.Parser (NIO ())
 parseCommand =