[PATCH STABLE v2] chmod: create a new file when flags are set on a hardlinked file

[Koen Van Hoof]

# HG changeset patch
# User Koen Van Hoof <koen.van_hoof at nokia.com>
# Date 1493215522 -7200
#      Wed Apr 26 16:05:22 2017 +0200
# Branch stable
# Node ID 04b33b356260d9d4c27f8cd223c7e5446a51ac48
# Parent  2de67783dd31c66be1677aa443b95eabb0129a75
chmod: create a new file when flags are set on a hardlinked file

For performance reasons we have several repositories where the files in the working
directory of 1 repo are hardlinks to the files of the other repo
When an update in one repo results in a chmod of a such a file, the hardlink
has to be deleted and replaced by a regular file to make sure that the change
does not happen in the other repo

diff --git a/mercurial/posix.py b/mercurial/posix.py
--- a/mercurial/posix.py
+++ b/mercurial/posix.py
@@ -98,7 +98,8 @@ def isexec(f):
     return (os.lstat(f).st_mode & 0o100 != 0)
 
 def setflags(f, l, x):
-    s = os.lstat(f).st_mode
+    st = os.lstat(f)
+    s = st.st_mode
     if l:
         if not stat.S_ISLNK(s):
             # switch file to link
@@ -124,6 +125,14 @@ def setflags(f, l, x):
         fp.close()
         s = 0o666 & ~umask # avoid restatting for chmod
 
+    if st.st_nlink > 1: # the file is a hardlink, break the hardlink
+        fpin = open(f,"r")
+        unlink(f)
+        fpout = open(f, "w")
+        fpout.write(fpin.read())
+        fpin.close()
+        fpout.close()
+
     sx = s & 0o100
     if x and not sx:
         # Turn on +x for every +r bit when making a file executable
@@ -132,6 +141,8 @@ def setflags(f, l, x):
     elif not x and sx:
         # Turn off all +x bits
         os.chmod(f, s & 0o666)
+    elif st.st_nlink > 1: # new file still needs its stat to be copied
+        os.chmod(f, s)
 
 def copymode(src, dst, mode=None):
     '''Copy the file mode from the file at path src to dst.
diff --git a/tests/test-hardlinks.t b/tests/test-hardlinks.t
--- a/tests/test-hardlinks.t
+++ b/tests/test-hardlinks.t
@@ -193,11 +193,18 @@ Committing a change to f1 in r1 must bre
   1 r2/.hg/store/data/f1.i
   [12] r2/\.hg/store/fncache (re)
 
+Create a file which exec permissions we will change
+  $ cd r3
+  $ echo "echo hello world" > f3
+  $ hg add f3
+  $ hg ci -mf3
+  $ cd ..
 
   $ cd r3
   $ hg tip --template '{rev}:{node|short}\n'
-  11:a6451b6bc41f
+  12:d3b77733a28a
   $ echo bla > f1
+  $ chmod +x f3
   $ hg ci -m1
   $ cd ..
 
@@ -226,6 +233,7 @@ r4 has hardlinks in the working dir (not
   2 r4/.hg/store/data/d1/f2.d
   2 r4/.hg/store/data/d1/f2.i
   2 r4/.hg/store/data/f1.i
+  2 r4/.hg/store/data/f3.i
   2 r4/.hg/store/fncache
   2 r4/.hg/store/phaseroots
   2 r4/.hg/store/undo
@@ -241,11 +249,12 @@ r4 has hardlinks in the working dir (not
   2 r4/d1/data1
   2 r4/d1/f2
   2 r4/f1
+  2 r4/f3
 
-Update back to revision 11 in r4 should break hardlink of file f1:
+Update back to revision 12 in r4 should break hardlink of file f1 and f3:
 
-  $ hg -R r4 up 11
-  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ hg -R r4 up 12
+  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
 
   $ nlinksdir r4
   2 r4/.hg/00changelog.i
@@ -265,6 +274,7 @@ Update back to revision 11 in r4 should 
   2 r4/.hg/store/data/d1/f2.d
   2 r4/.hg/store/data/d1/f2.i
   2 r4/.hg/store/data/f1.i
+  2 r4/.hg/store/data/f3.i
   2 r4/.hg/store/fncache
   2 r4/.hg/store/phaseroots
   2 r4/.hg/store/undo
@@ -280,6 +290,7 @@ Update back to revision 11 in r4 should 
   2 r4/d1/data1
   2 r4/d1/f2
   1 r4/f1
+  1 r4/f3
 
 
 Test hardlinking outside hg: