update: warn about other topological heads on bare update

A concern around the user experience of Mercurial is user getting stuck on there
own topological branch forever. For example, someone pulling another topological
branch, missing that message in pull asking them to merge and getting stuck on
there own local branch.

The current way to "address" this concern was for bare 'hg update' to target the
tipmost (also latest pulled) changesets and complain when the update was not
linear. That way, failure to merge newly pulled changesets would result in some
kind of failure.

Yet the failure was quite obscure, not working in all cases (eg: commit right
after pull) and the behavior was very impractical in the common case
(eg: issue4673).

To be able to change that behavior, we need to provide other ways to alert a
user stucks on one of many topological head. We do so with an extra message after
bare update:

  1 other heads for branch "default"

Bookmark get its own special version:

  1 other divergent bookmarks for "foobar"

There is significant room to improve the message itself, and we should augment
it with hint about how to see theses other heads or handle the situation (see
in-line comment). But having "a" message is already a significant improvement
compared to the existing situation. Once we have it we can iterate on a better
version of it. As having such message is an important step toward changing the
default destination for update and other nicety, I would like to move forward
quickly on getting such message.

This was discussed during London - October 2015 Sprint.

mercurial/commands.py

@@ -6955,6 +6955,8 b' def update(ui, repo, node=None, rev=None'
     if rev is None or rev == '':
         rev = node
 
+    warndest = False
+
     with repo.wlock():
         cmdutil.clearunfinished(repo)
 
@@ -6976,6 +6978,7 b' def update(ui, repo, node=None, rev=None'
         if rev is None:
             updata = destutil.destupdate(repo, clean=clean, check=check)
             rev, movemarkfrom, brev = updata
+            warndest = True
 
         repo.ui.setconfig('ui', 'forcemerge', tool, 'update')
 
@@ -7002,7 +7005,8 b' def update(ui, repo, node=None, rev=None'
                 ui.status(_("(leaving bookmark %s)\n") %
                           repo._activebookmark)
             bookmarks.deactivate(repo)
-
+        if warndest:
+            destutil.statusotherdests(ui, repo)
     return ret
 
 @command('verify', [])

mercurial/destutil.py

@@ -218,3 +218,34 b' def desthistedit(ui, repo):'
             return revs.first()
 
     return None
+
+def _statusotherbook(ui, repo):
+    bmheads = repo.bookmarkheads(repo._activebookmark)
+    curhead = repo[repo._activebookmark].node()
+    if repo.revs('%n and parents()', curhead):
+        # we are on the active bookmark
+        bmheads = [b for b in bmheads if curhead != b]
+        if bmheads:
+            msg = _('%i other divergent bookmarks for "%s"\n')
+            ui.status(msg % (len(bmheads), repo._activebookmark))
+
+def _statusotherbranchheads(ui, repo):
+    currentbranch = repo.dirstate.branch()
+    heads = repo.branchheads(currentbranch)
+    l = len(heads)
+    if repo.revs('%ln and parents()', heads):
+        # we are on a head
+        heads = repo.revs('%ln - parents()', heads)
+        if heads and l != len(heads):
+            ui.status(_('%i other heads for branch "%s"\n') %
+                      (len(heads), currentbranch))
+
+def statusotherdests(ui, repo):
+    """Print message about other head"""
+    # XXX we should probably include a hint:
+    # - about what to do
+    # - how to see such heads
+    if repo._activebookmark:
+        _statusotherbook(ui, repo)
+    else:
+        _statusotherbranchheads(ui, repo)

tests/test-bisect2.t

@@ -244,6 +244,7 b' hg up -C'
 
   $ hg up -C
   0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  3 other heads for branch "default"
 
 complex bisect test 1  # first bad rev is 9
 

tests/test-blackbox.t

@@ -123,6 +123,7 b' extension and python hooks - use the eol'
   $ hg update
   hooked
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  1 other heads for branch "default"
   $ hg blackbox -l 6
   1970/01/01 00:00:00 bob (*)> update (glob)
   1970/01/01 00:00:00 bob (*)> writing .hg/cache/tags2-visible with 0 tags (glob)

tests/test-bookmarks.t

@@ -573,6 +573,7 b' pull --update works the same as pull && '
   $ hg bookmark -r3 Y
   moving bookmark 'Y' forward from db815d6d32e6
   $ cp -r  ../cloned-bookmarks-update ../cloned-bookmarks-manual-update
+  $ cp -r  ../cloned-bookmarks-update ../cloned-bookmarks-manual-update-with-divergence
 
 (manual version)
 
@@ -617,6 +618,34 b' pull --update works the same as pull && '
   updating to active bookmark Y
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
 
+We warn about divergent during bare update to the active bookmark
+
+  $ hg -R ../cloned-bookmarks-manual-update-with-divergence update Y
+  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  (activating bookmark Y)
+  $ hg -R ../cloned-bookmarks-manual-update-with-divergence bookmarks -r X2 Y@1
+  $ hg -R ../cloned-bookmarks-manual-update-with-divergence bookmarks
+     X2                        1:925d80f479bb
+   * Y                         2:db815d6d32e6
+     Y@1                       1:925d80f479bb
+     Z                         2:db815d6d32e6
+     x  y                      2:db815d6d32e6
+  $ hg -R ../cloned-bookmarks-manual-update-with-divergence pull
+  pulling from $TESTTMP
+  searching for changes
+  adding changesets
+  adding manifests
+  adding file changes
+  added 2 changesets with 2 changes to 2 files (+1 heads)
+  updating bookmark Y
+  updating bookmark Z
+  (run 'hg heads' to see heads, 'hg merge' to merge)
+  $ hg -R ../cloned-bookmarks-manual-update-with-divergence update
+  updating to active bookmark Y
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  (activating bookmark Y)
+  1 other divergent bookmarks for "Y"
+
 test wrongly formated bookmark
 
   $ echo '' >> .hg/bookmarks
@@ -715,6 +744,7 b' test non-linear update not clearing acti'
   $ hg up -C
   1 files updated, 0 files merged, 1 files removed, 0 files unresolved
   (leaving bookmark drop)
+  1 other heads for branch "default"
   $ hg sum
   parent: 2:db815d6d32e6 
    2

tests/test-conflict.t

@@ -232,6 +232,7 b' are merging, unlike :local and :other'
 
   $ hg up -C
   2 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  1 other heads for branch "default"
   $ printf "\n\nEnd of file\n" >> a
   $ hg ci -m "Add some stuff at the end"
   $ hg up -r 1
@@ -269,6 +270,7 b' Now test :merge-other and :merge-local'
 
   $ hg up -C
   1 files updated, 0 files merged, 1 files removed, 0 files unresolved
+  1 other heads for branch "default"
   $ hg merge --tool :merge-local
   merging a
   2 files updated, 0 files merged, 0 files removed, 0 files unresolved

tests/test-largefiles-cache.t

@@ -202,6 +202,7 b' Inject corruption into the largefiles st'
   large: data corruption in $TESTTMP/src/.hg/largefiles/e2fb5f2139d086ded2cb600d5a91a196e76bf020 with hash 6a7bb2556144babe3899b25e5428123735bb1e27 (glob)
   0 largefiles updated, 0 removed
   0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  2 other heads for branch "default"
   $ hg st
   ! large
   ? z

tests/test-largefiles-update.t

@@ -68,6 +68,7 b" we don't have to hash them again next ti"
 
   $ hg up
   0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  1 other heads for branch "default"
   $ hg debugdirstate --large --nodate
   n 644          7 set                 large1
   n 644         13 set                 large2
@@ -82,6 +83,7 b' prevents unnecessary hashing of content '
   n 644         13 set                 large2
   $ hg up
   0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  1 other heads for branch "default"
   $ hg debugdirstate --large --nodate
   n 644          7 set                 large1
   n 644         13 set                 large2

tests/test-merge-changedelete.t

@@ -111,6 +111,7 b' Interactive merge:'
 
   $ hg co -C
   1 files updated, 0 files merged, 1 files removed, 0 files unresolved
+  1 other heads for branch "default"
 
   $ hg merge --config ui.interactive=true <<EOF
   > c
@@ -171,6 +172,7 b' Interactive merge with bad input:'
 
   $ hg co -C
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  1 other heads for branch "default"
 
   $ hg merge --config ui.interactive=true <<EOF
   > foo
@@ -243,6 +245,7 b' Interactive merge with not enough input:'
 
   $ hg co -C
   2 files updated, 0 files merged, 1 files removed, 0 files unresolved
+  1 other heads for branch "default"
 
   $ hg merge --config ui.interactive=true <<EOF
   > d
@@ -301,6 +304,7 b' Choose local versions of files'
 
   $ hg co -C
   2 files updated, 0 files merged, 1 files removed, 0 files unresolved
+  1 other heads for branch "default"
 
   $ hg merge --tool :local
   0 files updated, 3 files merged, 0 files removed, 0 files unresolved
@@ -345,6 +349,7 b' Choose other versions of files'
 
   $ hg co -C
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  1 other heads for branch "default"
 
   $ hg merge --tool :other
   0 files updated, 2 files merged, 1 files removed, 0 files unresolved
@@ -389,6 +394,7 b' Fail'
 
   $ hg co -C
   2 files updated, 0 files merged, 1 files removed, 0 files unresolved
+  1 other heads for branch "default"
 
   $ hg merge --tool :fail
   0 files updated, 0 files merged, 0 files removed, 3 files unresolved
@@ -436,6 +442,7 b' Force prompts with no input (should be s'
 
   $ hg co -C
   1 files updated, 0 files merged, 1 files removed, 0 files unresolved
+  1 other heads for branch "default"
 
   $ hg merge --config ui.interactive=True --tool :prompt
   local changed file1 which remote deleted
@@ -491,6 +498,7 b' Force prompts'
 
   $ hg co -C
   1 files updated, 0 files merged, 1 files removed, 0 files unresolved
+  1 other heads for branch "default"
 
   $ hg merge --tool :prompt
   local changed file1 which remote deleted
@@ -544,6 +552,7 b' Choose to merge all files'
 
   $ hg co -C
   1 files updated, 0 files merged, 1 files removed, 0 files unresolved
+  1 other heads for branch "default"
 
   $ hg merge --tool :merge3
   local changed file1 which remote deleted

tests/test-merge-default.t

@@ -33,6 +33,7 b' Should fail because not at a head:'
 
   $ hg up
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  2 other heads for branch "default"
 
 Should fail because > 2 heads:
 

tests/test-merge-types.t

@@ -155,6 +155,7 b' Update to link without local change shou'
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
   $ hg up
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  1 other heads for branch "default"
   $ hg st
   ? a.orig
 
@@ -175,6 +176,7 b' Update to link with local change should '
   keep (l)ocal, take (o)ther, or leave (u)nresolved? u
   0 files updated, 0 files merged, 0 files removed, 1 files unresolved
   use 'hg resolve' to retry unresolved file merges
+  1 other heads for branch "default"
   [1]
   $ hg diff --git
   diff --git a/a b/a

tests/test-merge5.t

@@ -24,6 +24,7 b''
   $ hg revert b
   $ hg update -c
   0 files updated, 0 files merged, 1 files removed, 0 files unresolved
+  1 other heads for branch "default"
   $ mv a c
 
 Should abort:

tests/test-strip.t

@@ -287,6 +287,7 b' after strip of merge parent'
 
   $ hg up
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  1 other heads for branch "default"
   $ hg log -G
   @  changeset:   4:264128213d29
   |  tag:         tip

tests/test-subrepo.t

@@ -664,6 +664,7 b' update'
   $ cd ../t
   $ hg up -C # discard our earlier merge
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  2 other heads for branch "default"
   $ echo blah > t/t
   $ hg ci -m13
   committing subrepository t
@@ -677,6 +678,7 b' KeyError'
 
   $ hg up -C # discard changes
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  2 other heads for branch "default"
 
 pull
 
@@ -718,6 +720,7 b' should pull t'
   adding file changes
   added 1 changesets with 1 changes to 1 files
   0 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  2 other heads for branch "default"
   $ cat t/t
   blah
 
@@ -1185,6 +1188,7 b' Check hg update --clean'
   ? s/c
   $ hg update -C
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  2 other heads for branch "default"
   $ hg status -S
   ? s/b
   ? s/c

tests/test-transplant.t

@@ -409,6 +409,7 b" transplant -c shouldn't use an old chang"
 
   $ hg up -C
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  1 other heads for branch "default"
   $ rm added
   $ hg transplant --continue
   abort: no transplant to continue

tests/test-update-branches.t

@@ -167,6 +167,7 b' Cases are run as shown in that table, ro'
 
   $ norevtest '-c clean same'   clean 2 -c
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  1 other heads for branch "default"
   parent=3
 
   $ revtest '-cC dirty linear'  dirty 1 2 -cC