contrib: add compilation-mode linking for our test output

These regular expressions will cause compilation-mode buffers in emacs
to link to source when there are check-code errors in the output of a
.t test.

In the true tradition of this file, I also have no idea what I'm doing.

Differential Revision: https://phab.mercurial-scm.org/D6000

contrib/hg-test-mode.el

@@ -53,4 +53,11 b''
   (setq mode-name "hg-test")
   (run-hooks 'hg-test-mode-hook))
 
+(with-eval-after-load "compile"
+  ;; Link to source files in test-check-code.t violations.
+  (add-to-list 'compilation-error-regexp-alist-alist
+               '(hg-test-check-code-output
+                 "\\+  \\([^:\n]+\\):\\([0-9]+\\):$" 1 2))
+  (add-to-list 'compilation-error-regexp-alist 'hg-test-check-code-output))
+
 (provide 'hg-test-mode)