absorb: make it explicit if empty changeset was created

If the config rewrite.empty-successor=skip is set, a message "became empty and
was dropped" is shown if the changeset became empty. If the config
rewrite.empty-successor=keep is set, absorb may create changesets even if they
became empty. It’s probably a good idea to make that explicit. Therefore the
message is changed to be a combination of both: "became empty and became ...".

Repeating the word "became" is not very elegant. This results from the fact
that "became" was and is overloaded to indicate both the change from non-empty
to empty and the successor relation. In the combinated message, both meanings
are used in one sentence.

hgext/absorb.py

@@ -783,11 +783,10 b' class fixupstate(object):'
                 # nothing changed, nothing commited
                 nextp1 = ctx
                 continue
-            if (
-                self.skip_empty_successor
-                and ctx.files()
-                and self._willbecomenoop(memworkingcopy, ctx, nextp1)
-            ):
+            willbecomenoop = ctx.files() and self._willbecomenoop(
+                memworkingcopy, ctx, nextp1
+            )
+            if self.skip_empty_successor and willbecomenoop:
                 # changeset is no longer necessary
                 self.replacemap[ctx.node()] = None
                 msg = _(b'became empty and was dropped')
@@ -798,7 +797,14 b' class fixupstate(object):'
                 nextp1 = lastcommitted
                 self.replacemap[ctx.node()] = lastcommitted.node()
                 if memworkingcopy:
-                    msg = _(b'%d file(s) changed, became %s') % (
+                    if willbecomenoop:
+                        msg = _(
+                            b'%d file(s) changed, became empty '
+                            b'and became %s'
+                        )
+                    else:
+                        msg = _(b'%d file(s) changed, became %s')
+                    msg = msg % (
                         len(memworkingcopy),
                         self._ctx2str(lastcommitted),
                     )

tests/test-absorb.t

@@ -509,6 +509,7 b' Setting config rewrite.empty-successor=k'
   $ hg commit -m b3
   $ echo 4 >> b
   $ hg commit -m b4
+  $ hg commit -m empty --config ui.allowemptycommit=True
   $ echo 1 > b
   $ echo 3 >> a
   $ hg absorb -pn
@@ -527,16 +528,19 b' Setting config rewrite.empty-successor=k'
   1154859 b12
   bfafb49 a12
   $ hg absorb -av --config rewrite.empty-successor=keep | grep became
-  0:bfafb49242db: 1 file(s) changed, became 4:1a2de97fc652
-  1:115485984805: 2 file(s) changed, became 5:0c930dfab74c
-  2:30970dbf7b40: 2 file(s) changed, became 6:df6574ae635c
-  3:a393a58b9a85: 2 file(s) changed, became 7:ad4bd3462c9e
+  0:bfafb49242db: 1 file(s) changed, became 5:1a2de97fc652
+  1:115485984805: 2 file(s) changed, became 6:0c930dfab74c
+  2:30970dbf7b40: 2 file(s) changed, became empty and became 7:df6574ae635c
+  3:a393a58b9a85: 2 file(s) changed, became empty and became 8:ad4bd3462c9e
+  4:1bb0e8cff87a: 2 file(s) changed, became 9:2dbed75af996
   $ hg log -T '{rev} {desc}\n' -Gp
-  @  7 b4
+  @  9 empty
+  |
+  o  8 b4
   |
-  o  6 b3
+  o  7 b3
   |
-  o  5 b12
+  o  6 b12
   |  diff --git a/b b/b
   |  new file mode 100644
   |  --- /dev/null
@@ -544,7 +548,7 b' Setting config rewrite.empty-successor=k'
   |  @@ -0,0 +1,1 @@
   |  +1
   |
-  o  4 a12
+  o  5 a12
      diff --git a/a b/a
      new file mode 100644
      --- /dev/null