vc-hg-mergebase: Try a pull if first attempt fails

* lisp/vc/vc-hg.el (vc-hg-mergebase): If the first attempt
fails, execute a pull, then try again.
(vc-hg-incoming-revision): Use 'hg identify' not 'hg incoming'.

(cherry picked from commit 106048b06258e96764bcc3284893b10199b11b0b)

diff --git a/lisp/vc/vc-hg.el b/lisp/vc/vc-hg.el
index 76d5529ff452a0d57f718460f54cbd45aec898e2..80fad662530cf82eee4e91b8501c525459b3546b 100644 (file)
--- a/lisp/vc/vc-hg.el
+++ b/lisp/vc/vc-hg.el
@@ -1471,15 +1471,15 @@ This runs the command \"hg summary\"."
                      remote-location)))
 
 (defun vc-hg-incoming-revision (remote-location)
-  (let ((output (with-output-to-string
-                  ;; Exits 1 to mean nothing to pull.
-                  (vc-hg-command standard-output 1 nil
-                                 "incoming" "-qn" "--limit=1"
-                                 "--template={node}"
-                                 (and (not (string-empty-p remote-location))
-                                     remote-location)))))
-    (and (not (string-empty-p output))
-         output)))
+  ;; Use 'hg identify' like this, and not 'hg incoming', because this
+  ;; will give a sensible answer regardless of whether the incoming
+  ;; revision has been pulled yet.
+  (with-output-to-string
+    (vc-hg-command standard-output 0 nil "identify" "--id"
+                   (if (string-empty-p remote-location)
+                       "default"
+                     remote-location)
+                   "--template={node}")))
 
 ;; FIXME: Resolve issue with `vc-hg-mergebase' and then delete this.
 (defun vc-hg-log-outgoing (buffer remote-location)
@@ -1488,15 +1488,23 @@ This runs the command \"hg summary\"."
                  (and (not (string-empty-p remote-location))
                      remote-location)))
 
-;; FIXME: This works only when both rev1 and rev2 have already been pulled.
-;;        That means it can't do the work
-;;        `vc-default-log-incoming' and `vc-default-log-outgoing' need it to do.
 (defun vc-hg-mergebase (rev1 &optional rev2)
-  (or (vc-hg--run-log "{node}"
-                      (format "last(ancestors(%s) and ancestors(%s))"
-                              rev1 (or rev2 "tip"))
-                      nil)
-      (error "No common ancestor for merge base")))
+  (cl-flet
+      ((go ()
+         (with-output-to-string
+           (vc-hg-command standard-output 0 nil "log"
+                          (format "--rev=last(ancestors(%s) and ancestors(%s))"
+                                  rev1 (or rev2 "."))
+                          "--limit=1" "--template={node}"))))
+    ;; If the first attempt fails it may be because REV1 or REV2 has not
+    ;; yet been pulled, such as the case where REV1 is the incoming
+    ;; revision.  Unconditionally pull and try again because we can't
+    ;; distinguish a failure due to REV1 or REV2 having not yet been
+    ;; pulled from one where REV1 or REV2 don't exist at all.
+    (condition-case _ (go)
+      (error (vc-hg-command nil 0 nil "pull")
+             (condition-case _ (go)
+               (error (error "No common ancestor for merge base")))))))
 
 (defvar vc-hg-error-regexp-alist
   '(("^M \\(.+\\)" 1 nil nil 0))