fix: use compatible option for uniq

"uniq --count" doesn't exist on my machine (macOS v10.15.3, Catalina)
"uniq -c" is less explicit, but it seems more compatible.

Ideally, we would use a lib that would do an abstraction of the OS, so this can run on any system (e.g. Windows).

Author: nicoespeon

src/services/count-commits-per-file.ts

@@ -66,7 +66,8 @@ function buildCommand(directory, { firstParent, since }): string {
       "'*.[tj]s'"
     ].join(" "),
     "sort",
-    "uniq --count"
+    // --count might not be supported by all OS
+    "uniq -c"
   ].join(" | ");
 }