Fix a couple of CommentAsPatch issues. (#14804)

* CutDiffAroundLine makes the incorrect assumption that `---` and `+++` always represent part of the header of a diff.

This PR adds a flag to its parsing to prevent this problem and adds a streaming parsing technique to CutDiffAroundLine using an io.pipe instead of just sending data to an unbounded buffer.

Fix #14711

Signed-off-by: Andrew Thornton <art27@cantab.net>

* Handle unquoted comment patch files

When making comment patches unfortunately the patch does not always quote the filename
This makes the diff --git header ambiguous again.

This PR finally adds handling for ambiguity in to parse patch

Fix #14812

Signed-off-by: Andrew Thornton <art27@cantab.net>

* Add in testing for no error

There is no way currently for CutDiffAroundLine in this test to cause an
error however, it should still be tested.

Signed-off-by: Andrew Thornton <art27@cantab.net>

services/gitdiff/gitdiff_test.go

@@ -208,6 +208,66 @@ rename to a b/a a/file b/b file
 			oldFilename: "a b/file b/a a/file",
 			filename:    "a b/a a/file b/b file",
 		},
+		{
+			name: "ambiguous deleted",
+			gitdiff: `diff --git a/b b/b b/b b/b
+deleted file mode 100644
+index 92e798b..0000000
+--- a/b b/b` + "\t" + `
++++ /dev/null
+@@ -1 +0,0 @@
+-b b/b
+`,
+			oldFilename: "b b/b",
+			filename:    "b b/b",
+			addition:    0,
+			deletion:    1,
+		},
+		{
+			name: "ambiguous addition",
+			gitdiff: `diff --git a/b b/b b/b b/b
+new file mode 100644
+index 0000000..92e798b
+--- /dev/null
++++ b/b b/b` + "\t" + `
+@@ -0,0 +1 @@
++b b/b
+`,
+			oldFilename: "b b/b",
+			filename:    "b b/b",
+			addition:    1,
+			deletion:    0,
+		},
+		{
+			name: "rename",
+			gitdiff: `diff --git a/b b/b b/b b/b b/b b/b
+similarity index 100%
+rename from b b/b b/b b/b b/b
+rename to b
+`,
+			oldFilename: "b b/b b/b b/b b/b",
+			filename:    "b",
+		},
+		{
+			name: "ambiguous 1",
+			gitdiff: `diff --git a/b b/b b/b b/b b/b b/b
+similarity index 100%
+rename from b b/b b/b b/b b/b
+rename to b
+`,
+			oldFilename: "b b/b b/b b/b b/b",
+			filename:    "b",
+		},
+		{
+			name: "ambiguous 2",
+			gitdiff: `diff --git a/b b/b b/b b/b b/b b/b
+similarity index 100%
+rename from b b/b b/b b/b
+rename to b b/b
+`,
+			oldFilename: "b b/b b/b b/b",
+			filename:    "b b/b",
+		},
 		{
 			name: "minuses-and-pluses",
 			gitdiff: `diff --git a/minuses-and-pluses b/minuses-and-pluses
@@ -235,32 +295,32 @@ index 6961180..9ba1a00 100644
 		t.Run(testcase.name, func(t *testing.T) {
 			got, err := ParsePatch(setting.Git.MaxGitDiffLines, setting.Git.MaxGitDiffLineCharacters, setting.Git.MaxGitDiffFiles, strings.NewReader(testcase.gitdiff))
 			if (err != nil) != testcase.wantErr {
-				t.Errorf("ParsePatch() error = %v, wantErr %v", err, testcase.wantErr)
+				t.Errorf("ParsePatch(%q) error = %v, wantErr %v", testcase.name, err, testcase.wantErr)
 				return
 			}
 			gotMarshaled, _ := json.MarshalIndent(got, "  ", "  ")
 			if got.NumFiles != 1 {
-				t.Errorf("ParsePath() did not receive 1 file:\n%s", string(gotMarshaled))
+				t.Errorf("ParsePath(%q) did not receive 1 file:\n%s", testcase.name, string(gotMarshaled))
 				return
 			}
 			if got.TotalAddition != testcase.addition {
-				t.Errorf("ParsePath() does not have correct totalAddition %d, wanted %d", got.TotalAddition, testcase.addition)
+				t.Errorf("ParsePath(%q) does not have correct totalAddition %d, wanted %d", testcase.name, got.TotalAddition, testcase.addition)
 			}
 			if got.TotalDeletion != testcase.deletion {
-				t.Errorf("ParsePath() did not have correct totalDeletion %d, wanted %d", got.TotalDeletion, testcase.deletion)
+				t.Errorf("ParsePath(%q) did not have correct totalDeletion %d, wanted %d", testcase.name, got.TotalDeletion, testcase.deletion)
 			}
 			file := got.Files[0]
 			if file.Addition != testcase.addition {
-				t.Errorf("ParsePath() does not have correct file addition %d, wanted %d", file.Addition, testcase.addition)
+				t.Errorf("ParsePath(%q) does not have correct file addition %d, wanted %d", testcase.name, file.Addition, testcase.addition)
 			}
 			if file.Deletion != testcase.deletion {
-				t.Errorf("ParsePath() did not have correct file deletion %d, wanted %d", file.Deletion, testcase.deletion)
+				t.Errorf("ParsePath(%q) did not have correct file deletion %d, wanted %d", testcase.name, file.Deletion, testcase.deletion)
 			}
 			if file.OldName != testcase.oldFilename {
-				t.Errorf("ParsePath() did not have correct OldName %s, wanted %s", file.OldName, testcase.oldFilename)
+				t.Errorf("ParsePath(%q) did not have correct OldName %q, wanted %q", testcase.name, file.OldName, testcase.oldFilename)
 			}
 			if file.Name != testcase.filename {
-				t.Errorf("ParsePath() did not have correct Name %s, wanted %s", file.Name, testcase.filename)
+				t.Errorf("ParsePath(%q) did not have correct Name %q, wanted %q", testcase.name, file.Name, testcase.filename)
 			}
 		})
 	}