rebase: add flag to require destination

In some mercurial workflows, the default destination for rebase does not
always work well and can lead to confusing behavior. With this flag enabled,
every rebase command will require passing an explicit destination, eliminating
this confusion.

hgext/rebase.py

@@ -662,6 +662,16 b' def rebase(ui, repo, **opts):'
 
           hg rebase -r "branch(featureX)" -d 1.3 --keepbranches
 
+    Configuration Options:
+
+    You can make rebase require a destination if you set the following config
+    option:
+
+      [commands]
+      rebase.requiredest = False
+
+    Return Values:
+
     Returns 0 on success, 1 if nothing to rebase or there are
     unresolved conflicts.
 
@@ -675,6 +685,12 b' def rebase(ui, repo, **opts):'
 
         # Validate input and define rebasing points
         destf = opts.get('dest', None)
+
+        if ui.config('commands', 'rebase.requiredest', False):
+            if not destf:
+                raise error.Abort(_('you must specify a destination'),
+                                  hint=_('use: hg rebase -d REV'))
+
         srcf = opts.get('source', None)
         basef = opts.get('base', None)
         revf = opts.get('rev', [])

tests/test-rebase-base.t

@@ -391,3 +391,25 b' Multiple roots. Two children share two p'
    /
   o  0: A
   
+Require a destination
+  $ cat >> $HGRCPATH <<EOF
+  > [commands]
+  > rebase.requiredest = True
+  > EOF
+  $ hg init repo
+  $ cd repo
+  $ echo a >> a
+  $ hg commit -qAm aa
+  $ echo b >> b
+  $ hg commit -qAm bb
+  $ hg up ".^"
+  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
+  $ echo c >> c
+  $ hg commit -qAm cc
+  $ hg rebase
+  abort: you must specify a destination
+  (use: hg rebase -d REV)
+  [255]
+  $ hg rebase -d 1
+  rebasing 2:5db65b93a12b "cc" (tip)
+  saved backup bundle to $TESTTMP/repo/.hg/strip-backup/5db65b93a12b-4fb789ec-backup.hg (glob)