--- a/mercurial/patch.py	Mon Sep 05 08:29:36 2016 +0000
+++ b/mercurial/patch.py	Fri Aug 26 12:48:20 2016 +0200
@@ -669,6 +669,8 @@
                 self.mode = (False, False)
         if self.missing:
             self.ui.warn(_("unable to find '%s' for patching\n") % self.fname)
+            self.ui.warn(_("(use '--prefix' to apply patch relative to the "
+                           "current directory)\n"))
 
         self.hash = {}
         self.dirty = 0

--- a/tests/test-import-bypass.t	Mon Sep 05 08:29:36 2016 +0000
+++ b/tests/test-import-bypass.t	Fri Aug 26 12:48:20 2016 +0200
@@ -41,6 +41,7 @@
   $ hg import --bypass ../test.diff
   applying ../test.diff
   unable to find 'a' for patching
+  (use '--prefix' to apply patch relative to the current directory)
   abort: patch failed to apply
   [255]
   $ hg st

--- a/tests/test-import.t	Mon Sep 05 08:29:36 2016 +0000
+++ b/tests/test-import.t	Fri Aug 26 12:48:20 2016 +0200
@@ -1623,6 +1623,7 @@
   $ hg export --rev 'desc("extended jungle")' | hg import --partial -
   applying patch from stdin
   unable to find 'jungle' for patching
+  (use '--prefix' to apply patch relative to the current directory)
   1 out of 1 hunks FAILED -- saving rejects to file jungle.rej
   patch applied partially
   (fix the .rej files and run `hg commit --amend`)
@@ -1764,3 +1765,31 @@
   $ hg log --debug -r . | grep extra
   extra:       branch=default
   extra:       foo=bar
+
+Warn the user that paths are relative to the root of
+repository when file not found for patching
+
+  $ mkdir filedir
+  $ echo "file1" >> filedir/file1
+  $ hg add filedir/file1
+  $ hg commit -m "file1"
+  $ cd filedir
+  $ hg import -p 2 - <<EOF
+  > # HG changeset patch
+  > # User test
+  > # Date 0 0
+  > file2
+  > 
+  > diff --git a/filedir/file1 b/filedir/file1
+  > --- a/filedir/file1
+  > +++ b/filedir/file1
+  > @@ -1,1 +1,2 @@
+  >  file1
+  > +file2
+  > EOF
+  applying patch from stdin
+  unable to find 'file1' for patching
+  (use '--prefix' to apply patch relative to the current directory)
+  1 out of 1 hunks FAILED -- saving rejects to file file1.rej
+  abort: patch failed to apply
+  [255]

--- a/tests/test-mq-missingfiles.t	Mon Sep 05 08:29:36 2016 +0000
+++ b/tests/test-mq-missingfiles.t	Fri Aug 26 12:48:20 2016 +0200
@@ -42,6 +42,7 @@
   $ hg qpush
   applying changeb
   unable to find 'b' for patching
+  (use '--prefix' to apply patch relative to the current directory)
   2 out of 2 hunks FAILED -- saving rejects to file b.rej
   patch failed, unable to continue (try -v)
   patch failed, rejects left in working directory
@@ -147,6 +148,7 @@
   $ hg qpush
   applying changeb
   unable to find 'b' for patching
+  (use '--prefix' to apply patch relative to the current directory)
   1 out of 1 hunks FAILED -- saving rejects to file b.rej
   patch failed, unable to continue (try -v)
   patch failed, rejects left in working directory