--- a/mercurial/cmdutil.py	Sun Dec 17 18:28:15 2017 +0900
+++ b/mercurial/cmdutil.py	Sun Dec 17 18:43:05 2017 +0900
@@ -1514,7 +1514,7 @@
                     match.uipath(matchroot), uirelroot))
 
     if stat:
-        diffopts = diffopts.copy(context=0)
+        diffopts = diffopts.copy(context=0, noprefix=False)
         width = 80
         if not ui.plain():
             width = ui.termwidth()

--- a/tests/test-diffstat.t	Sun Dec 17 18:28:15 2017 +0900
+++ b/tests/test-diffstat.t	Sun Dec 17 18:43:05 2017 +0900
@@ -69,6 +69,57 @@
    file with spaces |  Bin 
    1 files changed, 0 insertions(+), 0 deletions(-)
 
+Filename without "a/" or "b/" (issue5759):
+
+  $ hg diff --config 'diff.noprefix=1' -c1 --stat --git
+   a |  3 +++
+   1 files changed, 3 insertions(+), 0 deletions(-)
+  $ hg diff --config 'diff.noprefix=1' -c2 --stat --git
+   c |  Bin 
+   d |    0 
+   2 files changed, 0 insertions(+), 0 deletions(-)
+
+  $ hg log --config 'diff.noprefix=1' -r '1:' -p --stat --git
+  changeset:   1:3a95b07bb77f
+  user:        test
+  date:        Thu Jan 01 00:00:00 1970 +0000
+  summary:     appenda
+  
+   a |  3 +++
+   1 files changed, 3 insertions(+), 0 deletions(-)
+  
+  diff --git a a
+  --- a
+  +++ a
+  @@ -211,3 +211,6 @@
+   a
+   a
+   a
+  +a
+  +a
+  +a
+  
+  changeset:   2:c60a6c753773
+  tag:         tip
+  user:        test
+  date:        Thu Jan 01 00:00:00 1970 +0000
+  summary:     createb
+  
+   c |  Bin 
+   d |    0 
+   2 files changed, 0 insertions(+), 0 deletions(-)
+  
+  diff --git c c
+  new file mode 100644
+  index e69de29bb2d1d6434b8b29ae775ad8c2e48c5391..f76dd238ade08917e6712764a16a22005a50573d
+  GIT binary patch
+  literal 1
+  Ic${MZ000310RR91
+  
+  diff --git d d
+  new file mode 100644
+  
+
 diffstat within directories:
 
   $ hg rm -f 'file with spaces'