feat: add --line-numbers config option

The line numbers toggle (L key) from umputun#21 was runtime-only.
This adds a CLI flag, env var, and config file option so users
can enable line numbers by default.

Author: alexander-akhmetov

.claude-plugin/skills/revdiff/references/config.md

@@ -25,6 +25,7 @@ Then uncomment and edit the values you want to change.
 | `--no-status-bar` | `REVDIFF_NO_STATUS_BAR` | Hide the status bar | `false` |
 | `--wrap` | `REVDIFF_WRAP` | Enable line wrapping in diff view | `false` |
 | `--collapsed` | `REVDIFF_COLLAPSED` | Start in collapsed diff mode | `false` |
+| `--line-numbers` | `REVDIFF_LINE_NUMBERS` | Show line numbers in diff gutter | `false` |
 | `--no-confirm-discard` | `REVDIFF_NO_CONFIRM_DISCARD` | Skip confirmation when discarding annotations with Q | `false` |
 | `--chroma-style` | `REVDIFF_CHROMA_STYLE` | Chroma color theme for syntax highlighting | `catppuccin-macchiato` |
 | `--theme` | `REVDIFF_THEME` | Load color theme from `~/.config/revdiff/themes/` | |

README.md

@@ -160,6 +160,7 @@ Positional arguments support several forms:
 | `--no-status-bar` | Hide the status bar, env: `REVDIFF_NO_STATUS_BAR` | `false` |
 | `--wrap` | Enable line wrapping in diff view, env: `REVDIFF_WRAP` | `false` |
 | `--collapsed` | Start in collapsed diff mode, env: `REVDIFF_COLLAPSED` | `false` |
+| `--line-numbers` | Show line numbers in diff gutter, env: `REVDIFF_LINE_NUMBERS` | `false` |
 | `--no-confirm-discard` | Skip confirmation when discarding annotations with Q, env: `REVDIFF_NO_CONFIRM_DISCARD` | `false` |
 | `--chroma-style` | Chroma color theme for syntax highlighting, env: `REVDIFF_CHROMA_STYLE` | `catppuccin-macchiato` |
 | `--theme` | Load color theme from `~/.config/revdiff/themes/`, env: `REVDIFF_THEME` | |

cmd/revdiff/main.go

@@ -36,6 +36,7 @@ type options struct {
 	NoConfirmDiscard bool     `long:"no-confirm-discard" ini-name:"no-confirm-discard" env:"REVDIFF_NO_CONFIRM_DISCARD" description:"skip confirmation prompt when discarding annotations with Q"`
 	Wrap             bool     `long:"wrap" ini-name:"wrap" env:"REVDIFF_WRAP" description:"enable line wrapping in diff view"`
 	Collapsed        bool     `long:"collapsed" ini-name:"collapsed" env:"REVDIFF_COLLAPSED" description:"start in collapsed diff mode"`
+	LineNumbers      bool     `long:"line-numbers" ini-name:"line-numbers" env:"REVDIFF_LINE_NUMBERS" description:"show line numbers in diff gutter"`
 	ChromaStyle      string   `long:"chroma-style" ini-name:"chroma-style" env:"REVDIFF_CHROMA_STYLE" default:"catppuccin-macchiato" description:"chroma style for syntax highlighting"`
 	AllFiles         bool     `long:"all-files" short:"A" no-ini:"true" description:"browse all git-tracked files, not just diffs"`
 	Exclude          []string `long:"exclude" short:"X" ini-name:"exclude" env:"REVDIFF_EXCLUDE" env-delim:"," description:"exclude files matching prefix (may be repeated)"`
@@ -286,6 +287,7 @@ func run(opts options) error {
 		NoConfirmDiscard: opts.NoConfirmDiscard,
 		Wrap:             opts.Wrap,
 		Collapsed:        opts.Collapsed,
+		LineNumbers:      opts.LineNumbers,
 		TabWidth:         opts.TabWidth,
 		Ref:              opts.ref(),
 		Staged:           opts.Staged,

cmd/revdiff/main_test.go

@@ -115,6 +115,31 @@ func TestParseArgs_Collapsed(t *testing.T) {
 	})
 }
 
+func TestParseArgs_LineNumbers(t *testing.T) {
+	t.Run("flag", func(t *testing.T) {
+		opts, err := parseArgs(append(noConfigArgs(t), "--line-numbers"))
+		require.NoError(t, err)
+		assert.True(t, opts.LineNumbers)
+	})
+
+	t.Run("env", func(t *testing.T) {
+		t.Setenv("REVDIFF_LINE_NUMBERS", "true")
+		opts, err := parseArgs(noConfigArgs(t))
+		require.NoError(t, err)
+		assert.True(t, opts.LineNumbers)
+	})
+
+	t.Run("config file", func(t *testing.T) {
+		cfgDir := t.TempDir()
+		cfgPath := filepath.Join(cfgDir, "config")
+		err := os.WriteFile(cfgPath, []byte("[Application Options]\nline-numbers = true\n"), 0o600)
+		require.NoError(t, err)
+		opts, err := parseArgs([]string{"--config", cfgPath})
+		require.NoError(t, err)
+		assert.True(t, opts.LineNumbers)
+	})
+}
+
 func TestParseArgs_OutputFlag(t *testing.T) {
 	opts, err := parseArgs([]string{"-o", "/tmp/out.txt"})
 	require.NoError(t, err)

site/docs.html

@@ -187,6 +187,7 @@ <h2 id="options">Options</h2>
                 <tr><td><code>--no-status-bar</code></td><td>Hide the status bar</td><td><code>false</code></td></tr>
                 <tr><td><code>--wrap</code></td><td>Enable line wrapping</td><td><code>false</code></td></tr>
                 <tr><td><code>--collapsed</code></td><td>Start in collapsed diff mode</td><td><code>false</code></td></tr>
+                <tr><td><code>--line-numbers</code></td><td>Show line numbers in diff gutter</td><td><code>false</code></td></tr>
                 <tr><td><code>--no-confirm-discard</code></td><td>Skip discard confirmation</td><td><code>false</code></td></tr>
                 <tr><td><code>--chroma-style</code></td><td>Syntax highlighting theme</td><td><code>catppuccin-macchiato</code></td></tr>
                 <tr><td><code>--theme</code></td><td>Load color theme from <code>~/.config/revdiff/themes/</code></td><td></td></tr>

ui/model.go

@@ -133,6 +133,7 @@ type ModelConfig struct {
 	NoConfirmDiscard bool           // skip confirmation prompt when discarding annotations
 	Wrap             bool           // enable line wrapping
 	Collapsed        bool           // start in collapsed diff mode
+	LineNumbers      bool           // show line numbers in diff gutter
 	Only             []string       // show only these files (match by exact path or path suffix)
 	WorkDir          string         // working directory for resolving absolute --only paths
 	Keymap           *keymap.Keymap // custom key bindings (nil uses defaults)
@@ -168,6 +169,7 @@ func NewModel(renderer Renderer, store *annotation.Store, highlighter SyntaxHigh
 		noStatusBar:      cfg.NoStatusBar,
 		noConfirmDiscard: cfg.NoConfirmDiscard,
 		wrapMode:         cfg.Wrap,
+		lineNumbers:      cfg.LineNumbers,
 		collapsed:        collapsedState{enabled: cfg.Collapsed},
 		focus:            paneTree,
 		treeWidthRatio:   cfg.TreeWidthRatio,

ui/model_test.go

@@ -433,6 +433,24 @@ func TestModel_CollapsedModeFromConfig(t *testing.T) {
 	})
 }
 
+func TestModel_LineNumbersFromConfig(t *testing.T) {
+	renderer := &mocks.RendererMock{
+		ChangedFilesFunc: func(string, bool) ([]string, error) { return nil, nil },
+		FileDiffFunc:     func(string, string, bool) ([]diff.DiffLine, error) { return nil, nil },
+	}
+	store := annotation.NewStore()
+
+	t.Run("line numbers enabled via config", func(t *testing.T) {
+		m := NewModel(renderer, store, noopHighlighter(), ModelConfig{LineNumbers: true, TreeWidthRatio: 2})
+		assert.True(t, m.lineNumbers)
+	})
+
+	t.Run("line numbers disabled by default", func(t *testing.T) {
+		m := NewModel(renderer, store, noopHighlighter(), ModelConfig{TreeWidthRatio: 2})
+		assert.False(t, m.lineNumbers)
+	})
+}
+
 func TestModel_StatusModeIcons(t *testing.T) {
 	t.Run("all icons always present", func(t *testing.T) {
 		m := testModel(nil, nil)