[clang-format-diff] Fix missing formatting for zero length git diff lines

If we only delete lines that are outer block statements (if, while, etc),
clang-format-diff.py can't format the statements inside the block statements.

An example to repro:
1. Delete the if statment at line 118 in llvm/lib/CodeGen/Analysis.cpp.
2. Run `git diff -U0 --no-color HEAD^ | clang/tools/clang-format/clang-format-diff.py -i -p1`

It fails to format the statement after if.

Differential Revision: https://reviews.llvm.org/D111273

clang/tools/clang-format/clang-format-diff.py

@@ -90,9 +90,11 @@ def main():
       line_count = 1
       if match.group(3):
         line_count = int(match.group(3))
-      if line_count == 0:
-        continue
-      end_line = start_line + line_count - 1
+      # Also format lines range if line_count is 0 in case of deleting
+      # surrounding statements.
+      end_line = start_line
+      if line_count != 0:
+        end_line += line_count - 1
       lines_by_file.setdefault(filename, []).extend(
           ['-lines', str(start_line) + ':' + str(end_line)])
 

clang/tools/clang-format/git-clang-format

@@ -321,8 +321,9 @@ def extract_lines(patch_file):
       line_count = 1
       if match.group(3):
         line_count = int(match.group(3))
-      if line_count > 0:
-        matches.setdefault(filename, []).append(Range(start_line, line_count))
+      if line_count == 0:
+        line_count = 1
+      matches.setdefault(filename, []).append(Range(start_line, line_count))
   return matches