fetchgitrevision: removed

It doesn't work and was last referred to in 5553546c21

pkgs/build-support/fetchgitrevision/default.nix

@@ -1,10 +0,0 @@
-runCommand: git: repository: branch:
-  import (runCommand "head-revision"
-    { buildInputs = [ git ];
-      dummy = builtins.currentTime;
-    }
-    ''
-      rev=$(git ls-remote ${repository} | grep "refs/${branch}$" | awk '{ print $1 }')
-      echo "[ \"$rev\" ]" > $out
-      echo Latest revision in ${branch} is $rev
-    '')

pkgs/top-level/all-packages.nix

@@ -144,8 +144,6 @@ with pkgs;
 
   fetchgitPrivate = callPackage ../build-support/fetchgit/private.nix { };
 
-  fetchgitrevision = import ../build-support/fetchgitrevision runCommand git;
-
   fetchgitLocal = callPackage ../build-support/fetchgitlocal { };
 
   fetchmtn = callPackage ../build-support/fetchmtn (config.fetchmtn or {});