pkg/vcs: fix repetitive change handling in BaseForDiff

The current implementation runs into problems if we modify the same file
several times in the patch series since the sequential blob hashes will
not be found in the reproducer.

Fix it by moving the check for already processed files up.

1 files changed, 25 insertions, 0 deletions

diff --git a/pkg/vcs/git_test.go b/pkg/vcs/git_test.go
index f2fd9e059..d867ed692 100644
--- a/pkg/vcs/git_test.go
+++ b/pkg/vcs/git_test.go
@@ -599,6 +599,31 @@ index fa49b07..01c887f 100644
 		require.NoError(t, err)
 		require.Nil(t, base)
 	})
+	t.Run("multiple modifications", func(t *testing.T) {
+		map1, _ := repo.repo.fileHashes(commit3.Hash, []string{"a.txt"})
+
+		twoDiffs := []byte(fmt.Sprintf(`diff --git a/a.txt b/a.txt
+index %s..1111111 100644
+--- a/a.txt
++++ b/a.txt
+@@ -1 +1 @@
+-update a.txt
++update a.txt again
+diff --git a/a.txt b/a.txt
+index 1111111..2222222 100644
+--- a/a.txt
++++ b/a.txt
+@@ -1 +1 @@
+-update a.txt again
++update a.txt again and again
+`, map1["a.txt"]))
+
+		base, err := repo.repo.BaseForDiff(twoDiffs, &debugtracer.TestTracer{T: t})
+		require.NoError(t, err)
+		require.Len(t, base, 1)
+
+		assert.Equal(t, commit3.Hash, base[0].Hash)
+	})
 }
 
 func TestBaseForDiffMerge(t *testing.T) {