bisect: move check_state into the bisect module

Now that the function is simpler, we resume our quest to move the logic into the
bisect module. In the process, we add basic documentation.

mercurial/commands.py

@@ -835,14 +835,6 b' def bisect(ui, repo, rev=None, extra=Non'
 
     Returns 0 on success.
     """
-    def checkstate(state):
-        if state['good'] and state['bad']:
-            return True
-        if not state['good']:
-            raise error.Abort(_('cannot bisect (no known good revisions)'))
-        else:
-            raise error.Abort(_('cannot bisect (no known bad revisions)'))
-
     # backward compatibility
     if rev in "good bad reset init".split():
         ui.warn(_("(use of 'hg bisect <cmd>' is deprecated)\n"))
@@ -913,7 +905,7 b' def bisect(ui, repo, rev=None, extra=Non'
                 rev = None # clear for future iterations
                 state[transition].append(ctx.node())
                 ui.status(_('changeset %d:%s: %s\n') % (ctx, ctx, transition))
-                checkstate(state)
+                hbisect.checkstate(state)
                 # bisect
                 nodes, changesets, bgood = hbisect.bisect(repo.changelog, state)
                 # update to next check
@@ -928,7 +920,7 b' def bisect(ui, repo, rev=None, extra=Non'
         hbisect.printresult(ui, repo, state, displayer, nodes, bgood)
         return
 
-    checkstate(state)
+    hbisect.checkstate(state)
 
     # actually bisect
     nodes, changesets, good = hbisect.bisect(repo.changelog, state)

mercurial/hbisect.py

@@ -177,6 +177,17 b' def resetstate(repo):'
     if repo.vfs.exists("bisect.state"):
         repo.vfs.unlink("bisect.state")
 
+def checkstate(state):
+    """check we have both 'good' and 'bad' to define a range
+
+    Raise Abort exception otherwise."""
+    if state['good'] and state['bad']:
+        return True
+    if not state['good']:
+        raise error.Abort(_('cannot bisect (no known good revisions)'))
+    else:
+        raise error.Abort(_('cannot bisect (no known bad revisions)'))
+
 def get(repo, status):
     """
     Return a list of revision(s) that match the given status: