patch 8.1.0375: cannot use diff mode with Cygwin diff.exe

Problem:    Cannot use diff mode with Cygwin diff.exe. (Igor Forca)
Solution:   Skip over unrecognized lines in the diff output.
diff --git a/src/diff.c b/src/diff.c
index 0055cba..59daf1e 100644
--- a/src/diff.c
+++ b/src/diff.c
@@ -1600,6 +1600,10 @@
 		    && (tag_fgets(linebuf, LBUFLEN, fd) == 0)
 		    && (STRNCMP(line, "@@ ", 3) == 0))
 		diffstyle = DIFF_UNIFIED;
+	    else
+		// Format not recognized yet, skip over this line.  Cygwin diff
+		// may put a warning at the start of the file.
+		continue;
 	}
 
 	if (diffstyle == DIFF_ED)
diff --git a/src/testdir/test_diffmode.vim b/src/testdir/test_diffmode.vim
index c3c1eaf..0022a73 100644
--- a/src/testdir/test_diffmode.vim
+++ b/src/testdir/test_diffmode.vim
@@ -519,7 +519,9 @@
   endif
 
   func DiffExpr()
-    silent exe '!diff ' . v:fname_in . ' ' . v:fname_new . '>' . v:fname_out
+    " Prepent some text to check diff type detection
+    call writefile(['warning', '  message'], v:fname_out)
+    silent exe '!diff ' . v:fname_in . ' ' . v:fname_new . '>>' . v:fname_out
   endfunc
   set diffexpr=DiffExpr()
   set diffopt=foldcolumn:0
diff --git a/src/version.c b/src/version.c
index ca6ac59..c103339 100644
--- a/src/version.c
+++ b/src/version.c
@@ -795,6 +795,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    375,
+/**/
     374,
 /**/
     373,