patch: include flag-only file changes in "special" while filtering patch (issue5864)

This patch fix the issue5864 (or maybe issue5865 too) which occurs during
split (or I should say at the time of filtering the hunks in interactive
mode) where user hits a not ending loop of "no changes to record".
And it's not only the case for split it will happen in every interactive
case for e.g. `hg commit -i` or `hg uncommit -i`

After looking into code I found that when filtering we have some
notation called "special" for the file headers which doesn't contain
any hunk and just contain the header (for e.g. newly added empty file
or deleted file) where the user cannot change the content of operation.

And I think we can put this "flag-only" file change in that same bucket
of "special". But I doubt a bit about the case when a file have flag change
and atleast one hunk then user won't be able to separate the flag change
from hunks.
Changed test file reflect the fixed behaviour.

Differential Revision: https://phab.mercurial-scm.org/D6058

mercurial/patch.py

@@ -863,7 +863,7 b' class header(object):'
     diff_re = re.compile('diff -r .* (.*)$')
     allhunks_re = re.compile('(?:index|deleted file) ')
     pretty_re = re.compile('(?:new file|deleted file) ')
-    special_re = re.compile('(?:index|deleted|copy|rename) ')
+    special_re = re.compile('(?:index|deleted|copy|rename|new mode) ')
     newfile_re = re.compile('(?:new file)')
 
     def __init__(self, header):

tests/test-split.t

@@ -732,30 +732,33 b' Testing the case in split when commiting'
   
 
 #if no-windows
-  $ printf 'y\ny\ny\n' | hg split
-  diff --git a/foo b/foo
-  old mode 100644
-  new mode 100755
-  examine changes to 'foo'? [Ynesfdaq?] y
-  
-  no changes to record
+  $ cat > $TESTTMP/messages <<EOF
+  > split 1
+  > EOF
+  $ printf 'y\n' | hg split
   diff --git a/foo b/foo
   old mode 100644
   new mode 100755
   examine changes to 'foo'? [Ynesfdaq?] y
   
-  no changes to record
-  diff --git a/foo b/foo
-  old mode 100644
-  new mode 100755
-  examine changes to 'foo'? [Ynesfdaq?] y
+  EDITOR: HG: Splitting 3a2125f0f4cb. Write commit message for the first split changeset.
+  EDITOR: make executable
+  EDITOR: 
+  EDITOR: 
+  EDITOR: HG: Enter commit message.  Lines beginning with 'HG:' are removed.
+  EDITOR: HG: Leave message empty to abort commit.
+  EDITOR: HG: --
+  EDITOR: HG: user: test
+  EDITOR: HG: branch 'default'
+  EDITOR: HG: changed foo
+  created new head
+  saved backup bundle to $TESTTMP/issue5864/.hg/strip-backup/3a2125f0f4cb-629e4432-split.hg (obsstore-off !)
   
-  no changes to record
-  diff --git a/foo b/foo
-  old mode 100644
-  new mode 100755
-  examine changes to 'foo'? [Ynesfdaq?] abort: response expected
-  [255]
+  $ hg log -G -T "{node|short} {desc}\n"
+  @  b154670c87da split 1
+  |
+  o  51f273a58d82 initial
+  
 #else
 
 TODO: Fix this on Windows. See issue 2020 and 5883