Fix custom patch operations on added files

Several custom patch commands on parts of an added file would fail with the
confusing error message "error: new file XXX depends on old contents". These
were dropping the custom patch from the original commit, moving the patch to a
new commit, moving it to a later commit, or moving it to the index.

We fix this by converting the patch header from an added file to a diff against
an empty file. We do this not just for the purpose of applying the patch, but
also for rendering it and copying it to the clip board. I'm not sure it matters
much in these cases, but it does feel more correct for a filtered patch to be
presented this way.

pkg/integration/tests/patch_building/move_to_index_from_added_file_with_conflict.go

@@ -0,0 +1,96 @@
+package patch_building
+
+import (
+	"github.com/jesseduffield/lazygit/pkg/config"
+	. "github.com/jesseduffield/lazygit/pkg/integration/components"
+)
+
+var MoveToIndexFromAddedFileWithConflict = NewIntegrationTest(NewIntegrationTestArgs{
+	Description:  "Move a patch from a file that was added in a commit to the index, causing a conflict",
+	ExtraCmdArgs: []string{},
+	Skip:         false,
+	SetupConfig:  func(config *config.AppConfig) {},
+	SetupRepo: func(shell *Shell) {
+		shell.EmptyCommit("first commit")
+
+		shell.CreateFileAndAdd("file1", "1st line\n2nd line\n3rd line\n")
+		shell.Commit("commit to move from")
+		shell.UpdateFileAndAdd("file1", "1st line\n2nd line changed\n3rd line\n")
+		shell.Commit("conflicting change")
+	},
+	Run: func(t *TestDriver, keys config.KeybindingConfig) {
+		t.Views().Commits().
+			Focus().
+			Lines(
+				Contains("conflicting change").IsSelected(),
+				Contains("commit to move from"),
+				Contains("first commit"),
+			).
+			SelectNextItem().
+			PressEnter()
+
+		t.Views().CommitFiles().
+			IsFocused().
+			Lines(
+				Contains("file1").IsSelected(),
+			).
+			PressEnter()
+
+		t.Views().PatchBuilding().
+			IsFocused().
+			SelectNextItem().
+			PressPrimaryAction()
+
+		t.Views().Information().Content(Contains("Building patch"))
+
+		t.Common().SelectPatchOption(Contains("Move patch out into index"))
+
+		t.Common().AcknowledgeConflicts()
+
+		t.Views().Files().
+			IsFocused().
+			Lines(
+				Contains("UU").Contains("file1"),
+			).
+			PressEnter()
+
+		t.Views().MergeConflicts().
+			IsFocused().
+			ContainsLines(
+				Contains("1st line"),
+				Contains("<<<<<<< HEAD"),
+				Contains("======="),
+				Contains("2nd line changed"),
+				Contains(">>>>>>>"),
+				Contains("3rd line"),
+			).
+			SelectNextItem().
+			PressPrimaryAction()
+
+		t.Common().ContinueOnConflictsResolved()
+
+		t.ExpectPopup().Alert().
+			Title(Equals("Error")).
+			Content(Contains("Applied patch to 'file1' with conflicts")).
+			Confirm()
+
+		t.Views().Files().
+			IsFocused().
+			Lines(
+				Contains("UU").Contains("file1"),
+			).
+			PressEnter()
+
+		t.Views().MergeConflicts().
+			TopLines(
+				Contains("1st line"),
+				Contains("<<<<<<< ours"),
+				Contains("2nd line changed"),
+				Contains("======="),
+				Contains("2nd line"),
+				Contains(">>>>>>> theirs"),
+				Contains("3rd line"),
+			).
+			IsFocused()
+	},
+})

pkg/integration/tests/patch_building/move_to_new_commit_from_added_file.go

@@ -0,0 +1,88 @@
+package patch_building
+
+import (
+	"github.com/jesseduffield/lazygit/pkg/config"
+	. "github.com/jesseduffield/lazygit/pkg/integration/components"
+)
+
+var MoveToNewCommitFromAddedFile = NewIntegrationTest(NewIntegrationTestArgs{
+	Description:  "Move a patch from a file that was added in a commit to a new commit",
+	ExtraCmdArgs: []string{},
+	Skip:         false,
+	SetupConfig:  func(config *config.AppConfig) {},
+	SetupRepo: func(shell *Shell) {
+		shell.EmptyCommit("first commit")
+
+		shell.CreateFileAndAdd("file1", "1st line\n2nd line\n3rd line\n")
+		shell.Commit("commit to move from")
+	},
+	Run: func(t *TestDriver, keys config.KeybindingConfig) {
+		t.Views().Commits().
+			Focus().
+			Lines(
+				Contains("commit to move from").IsSelected(),
+				Contains("first commit"),
+			).
+			PressEnter()
+
+		t.Views().CommitFiles().
+			IsFocused().
+			Lines(
+				Contains("file1").IsSelected(),
+			).
+			PressEnter()
+
+		t.Views().PatchBuilding().
+			IsFocused().
+			SelectNextItem().
+			PressPrimaryAction()
+
+		t.Views().Information().Content(Contains("Building patch"))
+
+		t.Common().SelectPatchOption(Contains("Move patch into new commit"))
+
+		t.ExpectPopup().CommitMessagePanel().
+			InitialText(Equals("")).
+			Type("new commit").Confirm()
+
+		t.Views().Commits().
+			IsFocused().
+			Lines(
+				Contains("new commit").IsSelected(),
+				Contains("commit to move from"),
+				Contains("first commit"),
+			).
+			PressEnter()
+
+		t.Views().CommitFiles().
+			IsFocused().
+			Lines(
+				Contains("M file1").IsSelected(),
+			).
+			Tap(func() {
+				t.Views().Main().ContainsLines(
+					Equals(" 1st line"),
+					Equals("+2nd line"),
+					Equals(" 3rd line"),
+				)
+			}).
+			PressEscape()
+
+		t.Views().Commits().
+			IsFocused().
+			NavigateToLine(Contains("commit to move from")).
+			PressEnter()
+
+		t.Views().CommitFiles().
+			IsFocused().
+			Lines(
+				Contains("A file1").IsSelected(),
+			).
+			Tap(func() {
+				t.Views().Main().ContainsLines(
+					Equals("+1st line"),
+					Equals("+3rd line"),
+				)
+			})
+	},
+})

pkg/integration/tests/patch_building/remove_parts_of_added_file.go

@@ -0,0 +1,56 @@
+package patch_building
+
+import (
+	"github.com/jesseduffield/lazygit/pkg/config"
+	. "github.com/jesseduffield/lazygit/pkg/integration/components"
+)
+
+var RemovePartsOfAddedFile = NewIntegrationTest(NewIntegrationTestArgs{
+	Description:  "Remove a custom patch from a file that was added in a commit",
+	ExtraCmdArgs: []string{},
+	Skip:         false,
+	SetupConfig:  func(config *config.AppConfig) {},
+	SetupRepo: func(shell *Shell) {
+		shell.EmptyCommit("first commit")
+
+		shell.CreateFileAndAdd("file1", "1st line\n2nd line\n3rd line\n")
+		shell.Commit("commit to remove from")
+	},
+	Run: func(t *TestDriver, keys config.KeybindingConfig) {
+		t.Views().Commits().
+			Focus().
+			Lines(
+				Contains("commit to remove from").IsSelected(),
+				Contains("first commit"),
+			).
+			PressEnter()
+
+		t.Views().CommitFiles().
+			IsFocused().
+			Lines(
+				Contains("A file1").IsSelected(),
+			).
+			PressEnter()
+
+		t.Views().PatchBuilding().
+			IsFocused().
+			SelectNextItem().
+			PressPrimaryAction()
+
+		t.Views().Information().Content(Contains("Building patch"))
+
+		t.Common().SelectPatchOption(Contains("Remove patch from original commit"))
+
+		t.Views().CommitFiles().
+			IsFocused().
+			Lines(
+				Contains("A file1").IsSelected(),
+			).
+			PressEscape()
+
+		t.Views().Main().ContainsLines(
+			Equals("+1st line"),
+			Equals("+3rd line"),
+		)
+	},
+})

pkg/integration/tests/patch_building/specific_selection.go

@@ -126,9 +126,8 @@ var SpecificSelection = NewIntegrationTest(NewIntegrationTestArgs{
 				t.Views().Secondary().ContainsLines(
 					// direct-file patch
 					Contains(`diff --git a/direct-file b/direct-file`),
-					Contains(`new file mode 100644`),
 					Contains(`index`),
-					Contains(`--- /dev/null`),
+					Contains(`--- a/direct-file`),
 					Contains(`+++ b/direct-file`),
 					Contains(`@@ -0,0 +1 @@`),
 					Contains(`+direct file content`),
@@ -149,9 +148,8 @@ var SpecificSelection = NewIntegrationTest(NewIntegrationTestArgs{
 					Contains(` 1f`),
 					// line-file patch
 					Contains(`diff --git a/line-file b/line-file`),
-					Contains(`new file mode 100644`),
 					Contains(`index`),
-					Contains(`--- /dev/null`),
+					Contains(`--- a/line-file`),
 					Contains(`+++ b/line-file`),
 					Contains(`@@ -0,0 +1,5 @@`),
 					Contains(`+2a`),

pkg/integration/tests/test_list.go

@@ -232,6 +232,7 @@ var tests = []*components.IntegrationTest{
 	patch_building.MoveToEarlierCommitFromAddedFile,
 	patch_building.MoveToEarlierCommitNoKeepEmpty,
 	patch_building.MoveToIndex,
+	patch_building.MoveToIndexFromAddedFileWithConflict,
 	patch_building.MoveToIndexPartOfAdjacentAddedLines,
 	patch_building.MoveToIndexPartial,
 	patch_building.MoveToIndexWithConflict,
@@ -239,9 +240,11 @@ var tests = []*components.IntegrationTest{
 	patch_building.MoveToLaterCommit,
 	patch_building.MoveToLaterCommitPartialHunk,
 	patch_building.MoveToNewCommit,
+	patch_building.MoveToNewCommitFromAddedFile,
 	patch_building.MoveToNewCommitFromDeletedFile,
 	patch_building.MoveToNewCommitPartialHunk,
 	patch_building.RemoveFromCommit,
+	patch_building.RemovePartsOfAddedFile,
 	patch_building.ResetWithEscape,
 	patch_building.SelectAllFiles,
 	patch_building.SpecificSelection,