Fix empty line handling in patch.lua

Interpret empty lines in hunk bodies as empty context lines, that is,
add a space to them. This is consistent with command-line patch tool
behaviour.

Fixes #434.

1 files changed, 6 insertions, 1 deletions

diff --git a/src/luarocks/tools/patch.lua b/src/luarocks/tools/patch.lua
index b53bad61..9e5074ad 100644
--- a/src/luarocks/tools/patch.lua
+++ b/src/luarocks/tools/patch.lua
@@ -200,8 +200,13 @@ function patch.read_patch(filename, data)
     if state == 'hunkbody' then
       -- skip hunkskip and hunkbody code until definition of hunkhead read
 
+      if line:match"^[\r\n]*$" then
+          -- prepend space to empty lines to interpret them as context properly
+          line = " " .. line
+      end
+
       -- process line first
-      if line:match"^[- +\\]" or line:match"^[\r\n]*$" then
+      if line:match"^[- +\\]" then
           -- gather stats about line endings
           local he = files.hunkends[nextfileno]
           if endswith(line, "\r\n") then