Improvements to contribution generation

- Parse Co-authored-by lines too. There's several contributors (mostly
   via weblate, but a few GH ones too) who weren't credited otherwise.

 - Add support for git mailmap, remapping some emails to a canonnical
   username. This allows us to remove some duplicates - nobody needs
   both SquidDev and "Jonathan Coates."

   I'm not making this file public, as it contains email addresses. This
   does mean that CI builds will still contain the full list with
   duplicates.

build.gradle

@@ -220,9 +220,32 @@ processResources {
     try {
         hash = ["git", "-C", projectDir, "rev-parse", "HEAD"].execute().text.trim()
 
-        def blacklist = ['GitHub', 'dan200', 'Daniel Ratcliffe']
+        def blacklist = ['GitHub', 'Daniel Ratcliffe', 'Weblate']
-        ["git", "-C", projectDir, "log", "--format=tformat:%an%n%cn"].execute().text.split('\n').each {
+
-            if (!blacklist.contains(it)) contributors.add(it)
+        // Extract all authors, commiters and co-authors from the git log.
+        def authors = ["git", "-C", projectDir, "log", "--format=tformat:%an <%ae>%n%cn <%ce>%n%(trailers:key=Co-authored-by,valueonly)"]
+            .execute().text.readLines().unique()
+
+        // We now pass this through git's mailmap to de-duplicate some authors.
+        def remapAuthors = ["git", "check-mailmap", "--stdin"].execute()
+        remapAuthors.withWriter { stdin ->
+            if (stdin !instanceof BufferedWriter) stdin = new BufferedWriter(stdin)
+
+            authors.forEach {
+                if (it == "") return
+                if (!it.endsWith(">")) it += ">" // Some commits have broken Co-Authored-By lines!
+                stdin.writeLine(it)
+            }
+            stdin.close()
+        }
+
+        // And finally extract out the actual name.
+        def emailRegex = ~/^([^<]+) <.+>$/
+        remapAuthors.text.readLines().forEach {
+            def matcher = it =~ emailRegex
+            matcher.find()
+            def name = matcher.group(1)
+            if (!blacklist.contains(name)) contributors.add(name)
         }
     } catch (Exception e) {
         e.printStackTrace()