Add option to show one-sided files as unified diffs

README.md

@@ -55,6 +55,16 @@ You can disable this with the `highlight-line-changes` setting:
 git config split-diffs.highlight-line-changes false
 ```
 
+### Unified diffs for one-sided files
+
+A file that only has additions, or only has deletions, leaves one half of a split diff empty. To show such files as unified diffs, and keep split diffs for files that have both, enable the `unify-one-sided-diffs` setting:
+
+```
+git config split-diffs.unify-one-sided-diffs true
+```
+
+This decides per file rather than per hunk, so each file's hunks are held back until the whole file has been read.
+
 ### Enable scrolling in the terminal
 
 ```sh

src/getConfig.ts

@@ -6,12 +6,14 @@ export type Config = Theme & {
     MIN_LINE_WIDTH: number;
     WRAP_LINES: boolean;
     HIGHLIGHT_LINE_CHANGES: boolean;
+    UNIFY_ONE_SIDED_DIFFS: boolean;
 };
 
 export const CONFIG_DEFAULTS: Omit<Config, keyof Theme> = {
     MIN_LINE_WIDTH: 80,
     WRAP_LINES: true,
     HIGHLIGHT_LINE_CHANGES: true,
+    UNIFY_ONE_SIDED_DIFFS: false,
 };
 
 export function getConfig(gitConfig: GitConfig): Config {

src/getGitConfig.test.ts

@@ -9,6 +9,7 @@ import {
 const DEFAULT_CONFIG: GitConfig = {
     WRAP_LINES: true,
     HIGHLIGHT_LINE_CHANGES: true,
+    UNIFY_ONE_SIDED_DIFFS: false,
     MIN_LINE_WIDTH: DEFAULT_MIN_LINE_WIDTH,
     THEME_NAME: DEFAULT_THEME_NAME,
     THEME_DIRECTORY: DEFAULT_THEME_DIRECTORY,
@@ -24,6 +25,7 @@ describe('getGitConfig', () => {
             getGitConfig(`
 split-diffs.wrap-lines=false
 split-diffs.highlight-line-changes=false
+split-diffs.unify-one-sided-diffs=true
 split-diffs.min-line-width=40
 split-diffs.theme-name=arctic
 split-diffs.theme-directory=/tmp
@@ -32,6 +34,7 @@ split-diffs.syntax-highlighting-theme=dark-plus
         ).toEqual({
             WRAP_LINES: false,
             HIGHLIGHT_LINE_CHANGES: false,
+            UNIFY_ONE_SIDED_DIFFS: true,
             MIN_LINE_WIDTH: 40,
             THEME_NAME: 'arctic',
             THEME_DIRECTORY: '/tmp',
@@ -57,6 +60,7 @@ split-diffs.syntax-highlighting-theme=nord
             getGitConfig(`
 split-diffs.wrap-lines=1
 split-diffs.highlight-line-changes=1
+split-diffs.unify-one-sided-diffs=1
 split-diffs.min-line-width=bar
 split-diffs.syntax-highlighting-theme=foo
 split-diffs.theme-name=baz

src/getGitConfig.ts

@@ -5,6 +5,7 @@ export type GitConfig = {
     MIN_LINE_WIDTH: number;
     WRAP_LINES: boolean;
     HIGHLIGHT_LINE_CHANGES: boolean;
+    UNIFY_ONE_SIDED_DIFFS: boolean;
     THEME_DIRECTORY: string;
     THEME_NAME: string;
     SYNTAX_HIGHLIGHTING_THEME?: string;
@@ -53,6 +54,7 @@ export function getGitConfig(configString: string): GitConfig {
         MIN_LINE_WIDTH: minLineWidth,
         WRAP_LINES: rawConfig['wrap-lines'] !== 'false',
         HIGHLIGHT_LINE_CHANGES: rawConfig['highlight-line-changes'] !== 'false',
+        UNIFY_ONE_SIDED_DIFFS: rawConfig['unify-one-sided-diffs'] === 'true',
         THEME_DIRECTORY:
             rawConfig['theme-directory'] ?? DEFAULT_THEME_DIRECTORY,
         THEME_NAME: rawConfig['theme-name'] ?? DEFAULT_THEME_NAME,

src/index.test.ts

@@ -24,6 +24,7 @@ const TEST_CONFIG: Config = {
     MIN_LINE_WIDTH: 60,
     WRAP_LINES: false,
     HIGHLIGHT_LINE_CHANGES: false,
+    UNIFY_ONE_SIDED_DIFFS: false,
     ...TEST_THEME,
 };
 
@@ -56,6 +57,10 @@ const CONFIG_OVERRIDES: Record<string, TestOverrides> = {
         DELETED_WORD_COLOR: { color: { r: 255, g: 0, b: 0, a: 255 } },
         INSERTED_WORD_COLOR: { color: { r: 0, g: 255, b: 0, a: 255 } },
     },
+    unifyOneSidedDiffs: {
+        MIN_LINE_WIDTH: 60,
+        UNIFY_ONE_SIDED_DIFFS: true,
+    },
     syntaxHighlighted: {
         MIN_LINE_WIDTH: 60,
         WRAP_LINES: false,
@@ -522,6 +527,55 @@ index 095ee29..439621e 100644
             ).toMatchSnapshot();
         });
 
+        test('commit with one-sided and two-sided files', async function () {
+            expect(
+                await transform(
+                    config,
+                    `
+commit 1111111111111111111111111111111111111111
+Author: Shrey Banga <banga.shrey@gmail.com>
+Date:   Sun Apr 11 15:25:34 2021 -0700
+
+    Mix of changes
+
+diff --git a/added.md b/added.md
+index 1111111..2222222 100644
+--- a/added.md
++++ b/added.md
+@@ -1,2 +1,3 @@
+ first
++inserted
+ second
+@@ -10,2 +11,3 @@
+ tenth
++another insert
+ eleventh
+diff --git a/mixed.md b/mixed.md
+index 3333333..4444444 100644
+--- a/mixed.md
++++ b/mixed.md
+@@ -1,3 +1,3 @@
+ first
++only inserted in this hunk
+ second
+-third
+@@ -10,3 +10,2 @@
+ tenth
+-only deleted in this hunk
+ eleventh
+diff --git a/deleted.md b/deleted.md
+index 5555555..6666666 100644
+--- a/deleted.md
++++ b/deleted.md
+@@ -1,3 +1,2 @@
+ first
+-removed
+ second
+`
+                )
+            ).toMatchSnapshot();
+        });
+
         test('merge commit with 2 parents', async function () {
             // Source: the TypeScript repo
             expect(

src/iterFormatHunk.ts

@@ -18,7 +18,8 @@ export async function* iterFormatHunk(
     context: Context,
     diffType: 'unified-diff' | 'combined-diff',
     hunkHeaderLine: string,
-    hunkParts: HunkPart[]
+    hunkParts: HunkPart[],
+    forceUnified: boolean = false
 ): AsyncIterable<FormattedString> {
     const { HUNK_HEADER_COLOR, SCREEN_WIDTH, MIN_LINE_WIDTH } = context;
 
@@ -37,7 +38,8 @@ export async function* iterFormatHunk(
     );
 
     // Only split diffs if there's enough room
-    const splitDiffs = SCREEN_WIDTH >= MIN_LINE_WIDTH * hunkParts.length;
+    const splitDiffs =
+        !forceUnified && SCREEN_WIDTH >= MIN_LINE_WIDTH * hunkParts.length;
 
     if (splitDiffs) {
         yield* iterFormatHunkSplit(context, hunkParts, changes);

src/iterSideBySideDiffs.ts

@@ -38,7 +38,7 @@ async function* iterSideBySideDiffsFormatted(
     context: Context,
     lines: AsyncIterable<string>
 ): AsyncIterable<FormattedString> {
-    const { HORIZONTAL_SEPARATOR } = context;
+    const { HORIZONTAL_SEPARATOR, UNIFY_ONE_SIDED_DIFFS } = context;
 
     let state: State = 'unknown';
 
@@ -56,13 +56,43 @@ async function* iterSideBySideDiffsFormatted(
     let hunkParts: HunkPart[] = [];
     let hunkHeaderLine: string = '';
     async function* yieldHunk(diffType: 'unified-diff' | 'combined-diff') {
+        if (diffType === 'unified-diff' && UNIFY_ONE_SIDED_DIFFS) {
+            // Whether a file is one-sided is only known once all its hunks
+            // have been read, so hold them until the file ends.
+            fileHunks.push({ hunkHeaderLine, hunkParts });
+            return;
+        }
         yield* iterFormatHunk(context, diffType, hunkHeaderLine, hunkParts);
         for (const hunkPart of hunkParts) {
             hunkPart.startLineNo = -1;
             hunkPart.lines = [];
         }
     }
 
+    // Hunks of the current file, held back when UNIFY_ONE_SIDED_DIFFS is set
+    let fileHunks: { hunkHeaderLine: string; hunkParts: HunkPart[] }[] = [];
+    async function* yieldFileHunks() {
+        const hasPrefix = (lines: (string | null)[], prefix: string) =>
+            lines.some((line) => line?.startsWith(prefix));
+        const hasDeletions = fileHunks.some(({ hunkParts: [partA] }) =>
+            hasPrefix(partA.lines, '-')
+        );
+        const hasInsertions = fileHunks.some(({ hunkParts: [, partB] }) =>
+            hasPrefix(partB.lines, '+')
+        );
+        const isOneSided = !(hasDeletions && hasInsertions);
+        for (const { hunkHeaderLine, hunkParts } of fileHunks) {
+            yield* iterFormatHunk(
+                context,
+                'unified-diff',
+                hunkHeaderLine,
+                hunkParts,
+                isOneSided
+            );
+        }
+        fileHunks = [];
+    }
+
     async function* flushPending() {
         if (state === 'unified-diff' || state === 'combined-diff') {
             yield* yieldFileName();
@@ -108,6 +138,12 @@ async function* iterSideBySideDiffsFormatted(
         // Handle state starts
         if (nextState) {
             yield* flushPending();
+            if (
+                nextState !== 'unified-diff-hunk-header' &&
+                nextState !== 'unified-diff-hunk-body'
+            ) {
+                yield* yieldFileHunks();
+            }
 
             switch (nextState) {
                 case 'commit-header':
@@ -309,6 +345,7 @@ async function* iterSideBySideDiffsFormatted(
     }
 
     yield* flushPending();
+    yield* yieldFileHunks();
 }
 
 export async function* iterSideBySideDiffs(

src/previewTheme.ts

@@ -12,6 +12,7 @@ const CONFIG = {
     MIN_LINE_WIDTH: 40,
     WRAP_LINES: true,
     HIGHLIGHT_LINE_CHANGES: true,
+    UNIFY_ONE_SIDED_DIFFS: false,
 };
 
 async function previewTheme(