line numbers should never be 0

pydiffchecker/line_shift_checker.py

@@ -29,7 +29,7 @@ class ShiftedLines(Sized, Iterable):
 
 class LineShiftChecker:
     SUBMODULE_MODE = '160000'
-    DIFF_BLOCK_REGEX = r'@@ -(\d+),(\d+) \+(\d+),(\d+) @@'
+    DIFF_BLOCK_REGEX = r'@@ -(\d+)(?:,\d+)? \+(\d+)(?:,\d+)? @@'
 
     def __init__(self, revision_since: str, revision_until: str) -> None:
         self.revision_since = revision_since
@@ -55,8 +55,8 @@ class LineShiftChecker:
         for line in process_output:
             matches = re.search(LineShiftChecker.DIFF_BLOCK_REGEX, line)
             if matches:
-                diff_block_src_start = int(matches.group(1))
+                diff_block_src_start = max(int(matches.group(1)), 1)  # line number should never be 0
-                diff_block_dst_start = int(matches.group(3))
+                diff_block_dst_start = max(int(matches.group(2)), 1)  # line number should never be 0
 
                 # fill shifted lines between 2 diff blocks
                 for i in range(0, diff_block_src_start - src_line_index):