Goto next/previous diff commands + minor cleanups (#2759)

* Comment fix & gofmt fix

* Goto next/previous diff commands

These commands will work in `git` repositories or whenever `set diff on` is
working. They are bound to `Alt-[` and `Alt-]` by default. I would prefer
`Alt-Up` and `Alt-Down`, but that's already taken.

There are no tests at the moment; I'm looking into writing some since that will
be needed for the rest of the plan to make
https://github.com/zyedidia/micro/discussions/2753 a reality. I'm not sure how
difficult that will be.

* Realign JSON in keybindings.md

internal/action/actions.go

@@ -1027,6 +1027,28 @@ func (h *BufPane) FindPrevious() bool {
 	return true
 }
 
+// DiffNext searches forward until the beginning of the next block of diffs
+func (h *BufPane) DiffNext() bool {
+	cur := h.Cursor.Loc.Y
+	dl, err := h.Buf.FindNextDiffLine(cur, true)
+	if err != nil {
+		return false
+	}
+	h.GotoLoc(buffer.Loc{0, dl})
+	return true
+}
+
+// DiffPrevious searches forward until the end of the previous block of diffs
+func (h *BufPane) DiffPrevious() bool {
+	cur := h.Cursor.Loc.Y
+	dl, err := h.Buf.FindNextDiffLine(cur, false)
+	if err != nil {
+		return false
+	}
+	h.GotoLoc(buffer.Loc{0, dl})
+	return true
+}
+
 // Undo undoes the last action
 func (h *BufPane) Undo() bool {
 	h.Buf.Undo()
@@ -1311,7 +1333,7 @@ func (h *BufPane) OpenFile() bool {
 	return true
 }
 
-// OpenFile opens a new file in the buffer
+// JumpLine asks the user to enter a line number to jump to
 func (h *BufPane) JumpLine() bool {
 	InfoBar.Prompt("> ", "goto ", "Command", nil, func(resp string, canceled bool) {
 		if !canceled {

internal/action/bufpane.go

@@ -708,6 +708,8 @@ var BufKeyActions = map[string]BufKeyAction{
 	"FindLiteral":               (*BufPane).FindLiteral,
 	"FindNext":                  (*BufPane).FindNext,
 	"FindPrevious":              (*BufPane).FindPrevious,
+	"DiffNext":                  (*BufPane).DiffNext,
+	"DiffPrevious":              (*BufPane).DiffPrevious,
 	"Center":                    (*BufPane).Center,
 	"Undo":                      (*BufPane).Undo,
 	"Redo":                      (*BufPane).Redo,

internal/action/defaults_darwin.go

@@ -41,6 +41,8 @@ var bufdefaults = map[string]string{
 	"Alt-F":          "FindLiteral",
 	"Ctrl-n":         "FindNext",
 	"Ctrl-p":         "FindPrevious",
+	"Alt-[":          "DiffPrevious|CursorStart",
+	"Alt-]":          "DiffNext|CursorEnd",
 	"Ctrl-z":         "Undo",
 	"Ctrl-y":         "Redo",
 	"Ctrl-c":         "CopyLine|Copy",

internal/action/defaults_other.go

@@ -1,3 +1,4 @@
+//go:build !darwin
 // +build !darwin
 
 package action
@@ -43,6 +44,8 @@ var bufdefaults = map[string]string{
 	"Alt-F":          "FindLiteral",
 	"Ctrl-n":         "FindNext",
 	"Ctrl-p":         "FindPrevious",
+	"Alt-[":          "DiffPrevious|CursorStart",
+	"Alt-]":          "DiffNext|CursorEnd",
 	"Ctrl-z":         "Undo",
 	"Ctrl-y":         "Redo",
 	"Ctrl-c":         "CopyLine|Copy",

internal/buffer/buffer.go

@@ -474,7 +474,7 @@ func (b *Buffer) GetName() string {
 	return name
 }
 
-//SetName changes the name for this buffer
+// SetName changes the name for this buffer
 func (b *Buffer) SetName(s string) {
 	b.name = s
 }
@@ -1211,6 +1211,41 @@ func (b *Buffer) DiffStatus(lineN int) DiffStatus {
 	return b.diff[lineN]
 }
 
+// FindNextDiffLine returns the line number of the next block of diffs.
+// If `startLine` is already in a block of diffs, lines in that block are skipped.
+func (b *Buffer) FindNextDiffLine(startLine int, forward bool) (int, error) {
+	if b.diff == nil {
+		return 0, errors.New("no diff data")
+	}
+	startStatus, ok := b.diff[startLine]
+	if !ok {
+		startStatus = DSUnchanged
+	}
+	curLine := startLine
+	for {
+		curStatus, ok := b.diff[curLine]
+		if !ok {
+			curStatus = DSUnchanged
+		}
+		if curLine < 0 || curLine > b.LinesNum() {
+			return 0, errors.New("no next diff hunk")
+		}
+		if curStatus != startStatus {
+			if startStatus != DSUnchanged && curStatus == DSUnchanged {
+				// Skip over the block of unchanged text
+				startStatus = DSUnchanged
+			} else {
+				return curLine, nil
+			}
+		}
+		if forward {
+			curLine++
+		} else {
+			curLine--
+		}
+	}
+}
+
 // SearchMatch returns true if the given location is within a match of the last search.
 // It is used for search highlighting
 func (b *Buffer) SearchMatch(pos Loc) bool {

runtime/help/keybindings.md

@@ -200,6 +200,8 @@ Find
 FindLiteral
 FindNext
 FindPrevious
+DiffPrevious
+DiffNext
 Undo
 Redo
 Copy
@@ -473,6 +475,8 @@ conventions for text editing defaults.
     "Alt-F":          "FindLiteral",
     "Ctrl-n":         "FindNext",
     "Ctrl-p":         "FindPrevious",
+    "Alt-[":          "DiffPrevious|CursorStart",
+    "Alt-]":          "DiffNext|CursorEnd",
     "Ctrl-z":         "Undo",
     "Ctrl-y":         "Redo",
     "Ctrl-c":         "CopyLine|Copy",
@@ -526,6 +530,7 @@ conventions for text editing defaults.
     "MouseMiddle":    "PastePrimary",
     "Ctrl-MouseLeft": "MouseMultiCursor",
 
+    // Multi-cursor bindings
     "Alt-n":        "SpawnMultiCursor",
     "AltShiftUp":   "SpawnMultiCursorUp",
     "AltShiftDown": "SpawnMultiCursorDown",