Also return hunks with only added lines from parseDiff

We aren't using them, yet, except for deciding whether to show the warning about
hunks with only added lines.

Add a bit of test coverage for parseDiff while we're at it.

pkg/gui/controllers/helpers/fixup_helper_test.go

@@ -0,0 +1,137 @@
+package helpers
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestFixupHelper_parseDiff(t *testing.T) {
+	scenarios := []struct {
+		name                     string
+		diff                     string
+		expectedDeletedLineHunks []*hunk
+		expectedAddedLineHunks   []*hunk
+	}{
+		{
+			name:                     "no diff",
+			diff:                     "",
+			expectedDeletedLineHunks: []*hunk{},
+			expectedAddedLineHunks:   []*hunk{},
+		},
+		{
+			name: "hunk with only deleted lines",
+			diff: `
+diff --git a/file1.txt b/file1.txt
+index 9ce8efb33..aaf2a4666 100644
+--- a/file1.txt
++++ b/file1.txt
+@@ -3 +2,0 @@ bbb
+-xxx
+`,
+			expectedDeletedLineHunks: []*hunk{
+				{
+					filename:     "file1.txt",
+					startLineIdx: 3,
+					numLines:     1,
+				},
+			},
+			expectedAddedLineHunks: []*hunk{},
+		},
+		{
+			name: "hunk with deleted and added lines",
+			diff: `
+diff --git a/file1.txt b/file1.txt
+index 9ce8efb33..eb246cf98 100644
+--- a/file1.txt
++++ b/file1.txt
+@@ -3 +3 @@ bbb
+-xxx
++yyy
+`,
+			expectedDeletedLineHunks: []*hunk{
+				{
+					filename:     "file1.txt",
+					startLineIdx: 3,
+					numLines:     1,
+				},
+			},
+			expectedAddedLineHunks: []*hunk{},
+		},
+		{
+			name: "hunk with only added lines",
+			diff: `
+diff --git a/file1.txt b/file1.txt
+index 9ce8efb33..fb5e469e7 100644
+--- a/file1.txt
++++ b/file1.txt
+@@ -4,0 +5,2 @@ ddd
++xxx
++yyy
+`,
+			expectedDeletedLineHunks: []*hunk{},
+			expectedAddedLineHunks: []*hunk{
+				{
+					filename:     "file1.txt",
+					startLineIdx: 4,
+					numLines:     2,
+				},
+			},
+		},
+		{
+			name: "several hunks in different files",
+			diff: `
+diff --git a/file1.txt b/file1.txt
+index 9ce8efb33..0632e41b0 100644
+--- a/file1.txt
++++ b/file1.txt
+@@ -2 +1,0 @@ aaa
+-bbb
+@@ -4 +3 @@ ccc
+-ddd
++xxx
+@@ -6,0 +6 @@ fff
++zzz
+diff --git a/file2.txt b/file2.txt
+index 9ce8efb33..0632e41b0 100644
+--- a/file2.txt
++++ b/file2.txt
+@@ -0,3 +1,0 @@ aaa
+-aaa
+-bbb
+-ccc
+`,
+			expectedDeletedLineHunks: []*hunk{
+				{
+					filename:     "file1.txt",
+					startLineIdx: 2,
+					numLines:     1,
+				},
+				{
+					filename:     "file1.txt",
+					startLineIdx: 4,
+					numLines:     1,
+				},
+				{
+					filename:     "file2.txt",
+					startLineIdx: 0,
+					numLines:     3,
+				},
+			},
+			expectedAddedLineHunks: []*hunk{
+				{
+					filename:     "file1.txt",
+					startLineIdx: 6,
+					numLines:     1,
+				},
+			},
+		},
+	}
+	for _, s := range scenarios {
+		t.Run(s.name, func(t *testing.T) {
+			deletedLineHunks, addedLineHunks := parseDiff(s.diff)
+			assert.Equal(t, s.expectedDeletedLineHunks, deletedLineHunks)
+			assert.Equal(t, s.expectedAddedLineHunks, addedLineHunks)
+		})
+	}
+}