Demonstrate that a diffstat is laid out for 80 columns

git scales the graph of a diffstat to the width of the terminal it is
talking to. A render that talks to no terminal tells it no width, so the
stat comes out narrower than the view it is shown in, wasting most of a
wide one.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

pkg/integration/tests/diff/stat_uses_the_view_width.go

@@ -0,0 +1,45 @@
+package diff
+
+import (
+	"strconv"
+	"strings"
+
+	"github.com/jesseduffield/lazygit/pkg/config"
+	. "github.com/jesseduffield/lazygit/pkg/integration/components"
+)
+
+var StatUsesTheViewWidth = NewIntegrationTest(NewIntegrationTestArgs{
+	Description:  "The diffstat of a commit is laid out to the width of the view showing it",
+	ExtraCmdArgs: []string{},
+	Skip:         false,
+	SetupConfig: func(cfg *config.AppConfig) {
+		// git's own diff, so that the render runs as a plain command rather
+		// than through a renderer.
+		cfg.GetUserConfig().Git.DiffRenderers = []config.DiffRendererConfig{
+			{Type: "rawGit"},
+		}
+	},
+	SetupRepo: func(shell *Shell) {
+		// Enough added lines that git scales the graph to the width it has,
+		// rather than drawing one mark per line.
+		lines := make([]string, 200)
+		for i := range lines {
+			lines[i] = "line " + strconv.Itoa(i)
+		}
+		shell.CreateFileAndAdd("file1", strings.Join(lines, "\n")+"\n")
+		shell.Commit("add file1")
+	},
+	Run: func(t *TestDriver, keys config.KeybindingConfig) {
+		t.Views().Commits().
+			Focus().
+			Lines(
+				Contains("add file1").IsSelected(),
+			)
+
+		t.Views().Main().
+			/* EXPECTED:
+			Content(MatchesRegexp(`(?m)^ file1 \| 200 \+{80,}$`))
+			ACTUAL: */
+			Content(MatchesRegexp(`(?m)^ file1 \| 200 \+{60,70}$`))
+	},
+})

pkg/integration/tests/test_list.go

@@ -230,6 +230,7 @@ var tests = []*components.IntegrationTest{
 	diff.DiffNonStickyRange,
 	diff.IgnoreWhitespace,
 	diff.RenameSimilarityThresholdChange,
+	diff.StatUsesTheViewWidth,
 	file.ClickArrowToCollapse,
 	file.CollapseExpand,
 	file.CopyMenu,