update: use higher level wording for "crosses branches" error

When using "hg update" to update to a revision on another branch, if
the user has uncommitted changes in the working directory, hg aborts
with the following message:

  abort: crosses branches (use 'hg merge' to merge or use 'hg update
  -C' to discard changes)

If the user isn't trying to update to tip and they follow the command
examples verbatim, they would end up updating to the wrong revision.

This patch removes the command examples in favor of just telling the
user to either merge or use --clean:

  abort: crosses branches (merge branches or use --clean to discard
  changes)

hg also aborts if the user tries to use "hg update" to get to tip
(without specifying a revision) and tip is on another branch:

  abort: crosses branches (use 'hg merge' or use 'hg update -c')

This message is changed in the same fashion:

  abort: crosses branches (merge branches or use --check to force
  update)

mercurial/merge.py

@@ -502,11 +502,11 b' def update(repo, node, branchmerge, forc'
             if pa == p1 or pa == p2: # linear
                 pass # all good
             elif wc.files() or wc.deleted():
-                raise util.Abort(_("crosses branches (use 'hg merge' to merge "
-                                 "or use 'hg update -C' to discard changes)"))
+                raise util.Abort(_("crosses branches (merge branches or use"
+                                   " --clean to discard changes)"))
             elif onode is None:
-                raise util.Abort(_("crosses branches (use 'hg merge' or use "
-                                   "'hg update -c')"))
+                raise util.Abort(_("crosses branches (merge branches or use"
+                                   " --check to force update)"))
             else:
                 # Allow jumping branches if clean and specific rev given
                 overwrite = True

tests/test-merge5.t

@@ -14,7 +14,7 b''
   $ hg update 1
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
   $ hg update
-  abort: crosses branches (use 'hg merge' or use 'hg update -c')
+  abort: crosses branches (merge branches or use --check to force update)
   [255]
   $ hg update -c
   0 files updated, 0 files merged, 1 files removed, 0 files unresolved
@@ -27,7 +27,7 b' or delete".'
 Should abort:
 
   $ hg update -y 1
-  abort: crosses branches (use 'hg merge' to merge or use 'hg update -C' to discard changes)
+  abort: crosses branches (merge branches or use --clean to discard changes)
   [255]
   $ mv c a
 

tests/test-up-local-change.t

@@ -167,7 +167,7 b' create a second head'
   summary:     2
   
   $ hg --debug up
-  abort: crosses branches (use 'hg merge' to merge or use 'hg update -C' to discard changes)
+  abort: crosses branches (merge branches or use --clean to discard changes)
   [255]
   $ hg --debug merge
   abort: outstanding uncommitted changes (use 'hg status' to list changes)

tests/test-update-branches.t

@@ -77,7 +77,7 b' Cases are run as shown in that table, ro'
   parent=5
 
   $ norevtest 'none clean same'   clean 2
-  abort: crosses branches (use 'hg merge' or use 'hg update -c')
+  abort: crosses branches (merge branches or use --check to force update)
   parent=2
 
 
@@ -100,12 +100,12 b' Cases are run as shown in that table, ro'
   M foo
 
   $ revtest 'none dirty same'   dirty 2 3
-  abort: crosses branches (use 'hg merge' to merge or use 'hg update -C' to discard changes)
+  abort: crosses branches (merge branches or use --clean to discard changes)
   parent=2
   M foo
 
   $ revtest 'none dirty cross'  dirty 3 4
-  abort: crosses branches (use 'hg merge' to merge or use 'hg update -C' to discard changes)
+  abort: crosses branches (merge branches or use --clean to discard changes)
   parent=3
   M foo