git: fix the config output

When setting values using the `git config --set` command, git formats
the file a bit differently. This changes the output so it maps to that
format.

Differences:

* each `key = value` in a section is prefixed by a tab character
* the `=` between the key and the value is surrounded by spaces

modules/programs/git.nix

@@ -21,8 +21,8 @@ let
 
   # generation for multiple ini values
   mkKeyValue = k: v:
-    let mkKeyValue = generators.mkKeyValueDefault { } "=" k;
-    in concatStringsSep "\n" (map mkKeyValue (toList v));
+    let mkKeyValue = generators.mkKeyValueDefault { } " = " k;
+    in concatStringsSep "\n" (map (kv: "\t" + mkKeyValue kv) (toList v));
 
   # converts { a.b.c = 5; } to { "a.b".c = 5; } for toINI
   gitFlattenAttrs = let