Fix UNKNOWN being shown as git commit hash (#1533)

Fixes https://github.com/PostgREST/postgrest/issues/1530

CHANGELOG.md

@@ -9,6 +9,8 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 
 ### Fixed
 
+ - #1530, Fix how the PostgREST version is shown in the help text when the `.git` directory is not available - @monacoremo
+
 ## [7.0.1] - 2020-05-18
 
 ### Fixed

src/PostgREST/Config.hs

@@ -124,8 +124,12 @@ corsPolicy req = case lookup "origin" headers of
 -- | User friendly version number
 prettyVersion :: Text
 prettyVersion =
-  intercalate "." (map show $ versionBranch version)
-  <> " (" <> take 7 $(gitHash) <> ")"
+  intercalate "." (map show $ versionBranch version) <> gitRev
+  where
+    gitRev =
+      if $(gitHash) == "UNKNOWN"
+        then mempty
+        else " (" <> take 7 $(gitHash) <> ")"
 
 -- | Version number used in docs
 docsVersion :: Text