mull: Mull doesn't generate mutations for lines changed in specified Git diff.

Description

Mull doesn’t generate mutations for lines changed in specified Git diff.

sergeyb@pony:~/sources/mull_testing$ git show 580212eee09fdbe89fb00b6d577f026106d0a8aa
commit 580212eee09fdbe89fb00b6d577f026106d0a8aa
Author: Sergey Bronnikov <sergeyb@tarantool.org>
Date:   Mon Mar 22 11:15:30 2021 +0300

    add different statements to main

diff --git a/main.c b/main.c
index 67eb934..8405df3 100644
--- a/main.c
+++ b/main.c
@@ -4,6 +4,8 @@ void f1() {
     puts("abc");
     int a = 0;
     a = 2 + 2;
+    a = a + 2;
+    a = 2 + a;
 }
 
 int main() {

sergeyb@pony:~/sources/mull_testing$ mull-cxx --git-diff-ref 580212eee09fdbe89fb00b6d577f026106d0a8aa --git-project-root . ./main
[info] Extracting bitcode from executable (threads: 1)
       [################################] 1/1. Finished in 1ms
[info] Loading bitcode files (threads: 3)
       [################################] 3/3. Finished in 12ms
[info] Incremental testing using Git Diff is enabled.
- Git ref: 580212eee09fdbe89fb00b6d577f026106d0a8aa
- Git project root: .
[info] Sanity check run (threads: 1)
       [################################] 1/1. Finished in 2ms
[info] Gathering functions under test (threads: 1)
       [################################] 1/1. Finished in 0ms
[info] Applying function filter: no debug info (threads: 8)
       [################################] 10/10. Finished in 1ms
[info] Applying function filter: file path (threads: 4)
       [################################] 4/4. Finished in 0ms
[info] Instruction selection (threads: 4)
       [################################] 4/4. Finished in 10ms
[info] Searching mutants across functions (threads: 4)
       [################################] 4/4. Finished in 1ms
[info] Deduplicate mutants (threads: 1)
       [################################] 1/1. Finished in 0ms
[info] No mutants found. Mutation score: infinitely high
[info] Total execution time: 50ms
sergeyb@pony:~/sources/mull_testing$ 

How-to reproduce:

1. git clone https://github.com/ligurio/mull-testing
2. cd mull-testing
3. mull-cxx --git-diff-ref 580212eee09fdbe89fb00b6d577f026106d0a8aa --git-project-root . ./main

Version

sergeyb@pony:~/sources/mull_testing$ mull-cxx --version Mull: LLVM-based mutation testing https://github.com/mull-project/mull Version: 0.10.0-trunk1 Commit: 296ee8e Date: 10 Mar 2021 LLVM: 11.0.0