archive: report the node as "{p1node}+" when archiving a dirty wdir()

This is more useful than reporting all 'f's, allowing the archive to be diffed
against a specific revision to see what changed.

mercurial/archival.py

@@ -67,8 +67,14 def _rootctx(repo):
 def buildmetadata(ctx):
     '''build content of .hg_archival.txt'''
     repo = ctx.repo()
+    hex = ctx.hex()
+    if ctx.rev() is None:
+        hex = ctx.p1().hex()
+        if ctx.dirty():
+            hex += '+'
+
     base = 'repo: %s\nnode: %s\nbranch: %s\n' % (
-        _rootctx(repo).hex(), ctx.hex(), encoding.fromlocal(ctx.branch()))
+        _rootctx(repo).hex(), hex, encoding.fromlocal(ctx.branch()))
 
     tags = ''.join('tag: %s\n' % t for t in ctx.tags()
                    if repo.tagtype(t) == 'global')

tests/test-subrepo-deep-nested-change.t

@@ -187,6 +187,14 Archive wdir() with subrepos
   ../wdir/sub1/sub2/folder/test.txt
   ../wdir/sub1/sub2/sub2
 
+  $ cat ../wdir/.hg_archival.txt
+  repo: 7f491f53a367861f47ee64a80eb997d1f341b77a
+  node: 9bb10eebee29dc0f1201dcf5977b811a540255fd+
+  branch: default
+  latesttag: null
+  latesttagdistance: 4
+  changessincelatesttag: 3
+
 Attempting to archive 'wdir()' with a missing file is handled gracefully
   $ rm sub1/sub1
   $ rm -r ../wdir
@@ -204,6 +212,16 Attempting to archive 'wdir()' with a mi
 
 Continue relative path printing + subrepos
   $ hg update -Cq
+  $ rm -r ../wdir
+  $ hg archive -S -r 'wdir()' ../wdir
+  $ cat ../wdir/.hg_archival.txt
+  repo: 7f491f53a367861f47ee64a80eb997d1f341b77a
+  node: 9bb10eebee29dc0f1201dcf5977b811a540255fd
+  branch: default
+  latesttag: null
+  latesttagdistance: 4
+  changessincelatesttag: 3
+
   $ touch sub1/sub2/folder/bar
   $ hg addremove sub1/sub2
   adding sub1/sub2/folder/bar (glob)