Update runtime files.
diff --git a/runtime/doc/develop.txt b/runtime/doc/develop.txt
index e9c0ee9..28ba7cd 100644
--- a/runtime/doc/develop.txt
+++ b/runtime/doc/develop.txt
@@ -1,4 +1,4 @@
-*develop.txt* For Vim version 8.0. Last change: 2018 Apr 23
+*develop.txt* For Vim version 8.0. Last change: 2018 May 02
VIM REFERENCE MANUAL by Bram Moolenaar
@@ -18,7 +18,8 @@
code.
Vim is open source software. Everybody is encouraged to contribute to help
-improving Vim. For sending patches a context diff "diff -c" is preferred.
+improving Vim. For sending patches a unified diff "diff -u" is preferred.
+You can create a pull request on github, but it's not required.
Also see http://vim.wikia.com/wiki/How_to_make_and_submit_a_patch.
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