Autoload.

autoload/hunk.vim

@@ -0,0 +1,24 @@
+" number of lines [added, modified, removed]
+let s:summary = [0, 0, 0]
+
+function! hunk#summary()
+  return s:summary
+endfunction
+
+function! hunk#reset()
+  let s:summary = [0, 0, 0]  " TODO: is bling/airline expecting [-1, -1, -1]?
+endfunction
+
+function! hunk#increment_lines_added(count)
+  let s:summary[0] += a:count
+endfunction
+
+function! hunk#increment_lines_modified(count)
+  let s:summary[1] += a:count
+endfunction
+
+function! hunk#increment_lines_removed(count)
+  let s:summary[2] += a:count
+endfunction
+
+