diff --git a/doc/hgrc.5.txt b/doc/hgrc.5.txt
--- a/doc/hgrc.5.txt
+++ b/doc/hgrc.5.txt
@@ -648,7 +648,10 @@ command or with Mercurial Queues extensi
     When set to 'strict' patch content and patched files end of lines
     are preserved. When set to ``lf`` or ``crlf``, both files end of lines
     are ignored when patching and the result line endings are
-    normalized to either LF (Unix) or CRLF (Windows).
+    normalized to either LF (Unix) or CRLF (Windows). When set to
+    ``auto``, end of lines are again ignored while patching but line
+    endings in patched files are normalized to their original setting
+    on a per-file basis.
     Default: strict.
 
 
diff --git a/mercurial/patch.py b/mercurial/patch.py
--- a/mercurial/patch.py
+++ b/mercurial/patch.py
@@ -239,6 +239,7 @@ class linereader(object):
         self.fp = fp
         self.buf = []
         self.textmode = textmode
+        self.eol = None
 
     def push(self, line):
         if line is not None:
@@ -250,6 +251,11 @@ class linereader(object):
             del self.buf[0]
             return l
         l = self.fp.readline()
+        if not self.eol:
+            if l.endswith('\r\n'):
+                self.eol = '\r\n'
+            elif l.endswith('\n'):
+                self.eol = '\n'
         if self.textmode and l.endswith('\r\n'):
             l = l[:-2] + '\n'
         return l
@@ -264,13 +270,13 @@ class linereader(object):
 # @@ -start,len +start,len @@ or @@ -start +start @@ if len is 1
 unidesc = re.compile('@@ -(\d+)(,(\d+))? \+(\d+)(,(\d+))? @@')
 contextdesc = re.compile('(---|\*\*\*) (\d+)(,(\d+))? (---|\*\*\*)')
-eolmodes = ['strict', 'crlf', 'lf']
+eolmodes = ['strict', 'crlf', 'lf', 'auto']
 
 class patchfile(object):
     def __init__(self, ui, fname, opener, missing=False, eolmode='strict'):
         self.fname = fname
         self.eolmode = eolmode
-        self.eol = {'strict': None, 'crlf': '\r\n', 'lf': '\n'}[eolmode]
+        self.eol = None
         self.opener = opener
         self.ui = ui
         self.lines = []
@@ -298,7 +304,10 @@ class patchfile(object):
             return [os.readlink(fname)]
         fp = self.opener(fname, 'r')
         try:
-            return list(linereader(fp, self.eolmode != 'strict'))
+            lr = linereader(fp, self.eolmode != 'strict')
+            lines = list(lr)
+            self.eol = lr.eol
+            return lines
         finally:
             fp.close()
 
@@ -312,10 +321,17 @@ class patchfile(object):
         else:
             fp = self.opener(fname, 'w')
         try:
-            if self.eol and self.eol != '\n':
+            if self.eolmode == 'auto' and self.eol:
+                eol = self.eol
+            elif self.eolmode == 'crlf':
+                eol = '\r\n'
+            else:
+                eol = '\n'
+
+            if self.eolmode != 'strict' and eol != '\n':
                 for l in lines:
                     if l and l[-1] == '\n':
-                        l = l[:-1] + self.eol
+                        l = l[:-1] + eol
                     fp.write(l)
             else:
                 fp.writelines(lines)
diff --git a/tests/test-import-eol b/tests/test-import-eol
--- a/tests/test-import-eol
+++ b/tests/test-import-eol
@@ -28,19 +28,35 @@ echo '\.diff' > .hgignore
 python -c 'file("a", "wb").write("a\nbbb\ncc\n\nd\ne")'
 hg ci -Am adda
 python ../makepatch.py
+
 echo % invalid eol
 hg --config patch.eol='LFCR' import eol.diff
 hg revert -a
+
 echo % force LF
 hg --traceback --config patch.eol='LF' import eol.diff
 python -c 'print repr(file("a","rb").read())'
 hg st
+
 echo % force CRLF
 hg up -C 0
 hg --traceback --config patch.eol='CRLF' import eol.diff
 python -c 'print repr(file("a","rb").read())'
 hg st
 
+echo % auto EOL on LF file
+hg up -C 0
+hg --traceback --config patch.eol='auto' import eol.diff
+python -c 'print repr(file("a","rb").read())'
+hg st
+
+echo % auto EOL on CRLF file
+python -c 'file("a", "wb").write("a\r\nbbb\r\ncc\r\n\r\nd\r\ne")'
+hg commit -m 'switch EOLs in a'
+hg --traceback --config patch.eol='auto' import eol.diff
+python -c 'print repr(file("a","rb").read())'
+hg st
+
 # Test --eol and binary patches
 python -c 'file("b", "wb").write("a\x00\nb")'
 hg ci -Am addb
diff --git a/tests/test-import-eol.out b/tests/test-import-eol.out
--- a/tests/test-import-eol.out
+++ b/tests/test-import-eol.out
@@ -10,6 +10,13 @@ applying eol.diff
 1 files updated, 0 files merged, 0 files removed, 0 files unresolved
 applying eol.diff
 'a\r\nyyyy\r\ncc\r\n\r\nd\r\ne'
+% auto EOL on LF file
+1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+applying eol.diff
+'a\nyyyy\ncc\n\nd\ne'
+% auto EOL on CRLF file
+applying eol.diff
+'a\r\nyyyy\r\ncc\r\n\r\nd\r\ne'
 adding b
 % binary patch with --eol
 applying bin.diff