Add shortcuts to compare incoming/current with common ancestor

Git has a diff style `diff3` or `zdiff3` that shows the common ancestor of two conflicting commits in the conflict. For example: ``` <<<<<<< HEAD int c = 2; ||||||| parent of ed293d1 (Capitalise) int c; ======= int C; >>>>>>> ed293d1 (Capitalise) ``` This is enormously useful when resolving conflicts. However sometimes git is dumb and you end up with conflicts that are difficult to follow. For example suppose you have some `really long old code`, and you write some `new code` to replace it. You rebase your change, and find that someone has made a tiny tiny change *somewhere* in the really long old code. It *might* be relevant - it could be some change that you also need to apply to your new code. But the conflict just looks like this: ``` <<<<<<< HEAD really long old code ||||||| parent of ed293d1 (Capitalise) really Long old code ======= new code >>>>>>> ed293d1 (Capitalise) ``` Not too bad with 4 lines but sometimes it's hundreds, and then you end up visually diffing it, like a cave man. There is an existing `Compare Changes` option, but it only compares `Current` with `Incoming`. This commit adds two more options to compare the common ancestor with `Current` or `Incoming` instead, thus solving the problem once and for all. This was mostly straightforward. The two tricky bits are: 1. Apparently you can have more than one common ancestor. I've never seen that so I just don't show the buttons in that case (or pick the first common ancestor if you use the command palette). 2. What if you don't have `diff3` and still run the new compare commands from the command palette? In that case it falls back to not showing any changes.
microsoft · Dec 18, 2024 · 7323471 · 7323471
1 parent 929ce7c
commit 7323471
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diff --git a/extensions/merge-conflict/package.json b/extensions/merge-conflict/package.json
@@ -101,6 +101,20 @@
         "original": "Compare Current Conflict",
         "command": "merge-conflict.compare",
         "enablement": "!isMergeEditor"
+      },
+      {
+        "category": "%command.category%",
+        "title": "%command.compare-ancestor-current%",
+        "original": "Compare Current Conflict (common ancestor ↔ current)",
+        "command": "merge-conflict.compare-ancestor-current",
+        "enablement": "!isMergeEditor"
+      },
+      {
+        "category": "%command.category%",
+        "title": "%command.compare-ancestor-incoming%",
+        "original": "Compare Current Conflict (common ancestor ↔ incoming)",
+        "command": "merge-conflict.compare-ancestor-incoming",
+        "enablement": "!isMergeEditor"
       }
     ],
     "menus": {

diff --git a/extensions/merge-conflict/package.nls.json b/extensions/merge-conflict/package.nls.json
@@ -12,6 +12,8 @@
 	"command.next": "Next Conflict",
 	"command.previous": "Previous Conflict",
 	"command.compare": "Compare Current Conflict",
+	"command.compare-ancestor-current": "Compare Current Conflict (common ancestor ↔ current)",
+	"command.compare-ancestor-incoming": "Compare Current Conflict (common ancestor ↔ incoming)",
 	"config.title": "Merge Conflict",
 	"config.autoNavigateNextConflictEnabled": "Whether to automatically navigate to the next merge conflict after resolving a merge conflict.",
 	"config.codeLensEnabled": "Create a CodeLens for merge conflict blocks within editor.",

diff --git a/extensions/merge-conflict/src/codelensProvider.ts b/extensions/merge-conflict/src/codelensProvider.ts
@@ -63,25 +63,31 @@ export default class MergeConflictCodeLensProvider implements vscode.CodeLensPro
 		conflicts.forEach(conflict => {
 			const acceptCurrentCommand: vscode.Command = {
 				command: 'merge-conflict.accept.current',
-				title: vscode.l10n.t("Accept Current Change"),
+				title: vscode.l10n.t("Accept Current"),
 				arguments: ['known-conflict', conflict]
 			};
 
 			const acceptIncomingCommand: vscode.Command = {
 				command: 'merge-conflict.accept.incoming',
-				title: vscode.l10n.t("Accept Incoming Change"),
+				title: vscode.l10n.t("Accept Incoming"),
 				arguments: ['known-conflict', conflict]
 			};
 
 			const acceptBothCommand: vscode.Command = {
 				command: 'merge-conflict.accept.both',
-				title: vscode.l10n.t("Accept Both Changes"),
+				title: vscode.l10n.t("Accept Both"),
 				arguments: ['known-conflict', conflict]
 			};
 
+			// Only allow comparing with the common ancestor if there is a single
+			// one. This is the common case with diff3/zdiff3.
+			const hasSingleCommonAncestor = conflict.commonAncestors.length === 1;
+
 			const diffCommand: vscode.Command = {
 				command: 'merge-conflict.compare',
-				title: vscode.l10n.t("Compare Changes"),
+				title: hasSingleCommonAncestor
+					? vscode.l10n.t("Compare Current & Incoming")
+					: vscode.l10n.t("Compare Changes"),
 				arguments: [conflict]
 			};
 
@@ -92,6 +98,25 @@ export default class MergeConflictCodeLensProvider implements vscode.CodeLensPro
 				new vscode.CodeLens(range, acceptBothCommand),
 				new vscode.CodeLens(range, diffCommand)
 			);
+
+			if (hasSingleCommonAncestor) {
+				const diffBaseCurrentCommand: vscode.Command = {
+					command: 'merge-conflict.compare-ancestor-current',
+					title: vscode.l10n.t("Compare Ancestor & Current"),
+					arguments: [conflict]
+				};
+
+				const diffBaseIncomingCommand: vscode.Command = {
+					command: 'merge-conflict.compare-ancestor-incoming',
+					title: vscode.l10n.t("Compare Ancestor & Incoming"),
+					arguments: [conflict]
+				};
+
+				items.push(
+					new vscode.CodeLens(range, diffBaseCurrentCommand),
+					new vscode.CodeLens(range, diffBaseIncomingCommand),
+				);
+			}
 		});
 
 		return items;

diff --git a/extensions/merge-conflict/src/commandHandler.ts b/extensions/merge-conflict/src/commandHandler.ts
@@ -36,7 +36,9 @@ export default class CommandHandler implements vscode.Disposable {
 			this.registerTextEditorCommand('merge-conflict.accept.all-both', this.acceptAllBoth),
 			this.registerTextEditorCommand('merge-conflict.next', this.navigateNext),
 			this.registerTextEditorCommand('merge-conflict.previous', this.navigatePrevious),
-			this.registerTextEditorCommand('merge-conflict.compare', this.compare)
+			this.registerTextEditorCommand('merge-conflict.compare', this.compareCurrentIncoming),
+			this.registerTextEditorCommand('merge-conflict.compare-ancestor-current', this.compareAncestorCurrent),
+			this.registerTextEditorCommand('merge-conflict.compare-ancestor-incoming', this.compareAncestorIncoming),
 		);
 	}
 
@@ -82,7 +84,14 @@ export default class CommandHandler implements vscode.Disposable {
 		return this.acceptAll(interfaces.CommitType.Both, editor);
 	}
 
-	async compare(editor: vscode.TextEditor, conflict: interfaces.IDocumentMergeConflict | null) {
+	private async compare(
+		editor: vscode.TextEditor,
+		conflict: interfaces.IDocumentMergeConflict | null,
+		leftTitle: string,
+		leftRegion: (conflict: interfaces.IDocumentMergeConflict) => interfaces.IMergeRegion,
+		rightTitle: string,
+		rightRegion: (conflict: interfaces.IDocumentMergeConflict) => interfaces.IMergeRegion,
+	) {
 
 		// No conflict, command executed from command palette
 		if (!conflict) {
@@ -104,18 +113,18 @@ export default class CommandHandler implements vscode.Disposable {
 		}
 
 		const scheme = editor.document.uri.scheme;
-		let range = conflict.current.content;
-		const leftRanges = conflicts.map(conflict => [conflict.current.content, conflict.range]);
-		const rightRanges = conflicts.map(conflict => [conflict.incoming.content, conflict.range]);
+		const leftRanges = conflicts.map(conflict => [leftRegion(conflict)?.content, conflict.range]);
+		const rightRanges = conflicts.map(conflict => [rightRegion(conflict)?.content, conflict.range]);
 
 		const leftUri = editor.document.uri.with({
 			scheme: ContentProvider.scheme,
-			query: JSON.stringify({ scheme, range: range, ranges: leftRanges })
+			query: JSON.stringify({ scheme, ranges: leftRanges })
 		});
 
-
-		range = conflict.incoming.content;
-		const rightUri = leftUri.with({ query: JSON.stringify({ scheme, ranges: rightRanges }) });
+		const rightUri = editor.document.uri.with({
+			scheme: ContentProvider.scheme,
+			query: JSON.stringify({ scheme, ranges: rightRanges })
+		});
 
 		let mergeConflictLineOffsets = 0;
 		for (const nextconflict of conflicts) {
@@ -132,7 +141,7 @@ export default class CommandHandler implements vscode.Disposable {
 
 		const docPath = editor.document.uri.path;
 		const fileName = docPath.substring(docPath.lastIndexOf('/') + 1); // avoid NodeJS path to keep browser webpack small
-		const title = vscode.l10n.t("{0}: Current Changes ↔ Incoming Changes", fileName);
+		const title = `${fileName}: ${leftTitle} ↔ ${rightTitle}`;
 		const mergeConflictConfig = vscode.workspace.getConfiguration('merge-conflict');
 		const openToTheSide = mergeConflictConfig.get<string>('diffViewPosition');
 		const opts: vscode.TextDocumentShowOptions = {
@@ -147,6 +156,47 @@ export default class CommandHandler implements vscode.Disposable {
 		await vscode.commands.executeCommand('vscode.diff', leftUri, rightUri, title, opts);
 	}
 
+	compareCurrentIncoming(editor: vscode.TextEditor, conflict: interfaces.IDocumentMergeConflict | null) {
+		return this.compare(
+			editor,
+			conflict,
+			vscode.l10n.t("Current Changes"),
+			(conflict: interfaces.IDocumentMergeConflict) => conflict.current,
+			vscode.l10n.t("Incoming Changes"),
+			(conflict: interfaces.IDocumentMergeConflict) => conflict.incoming,
+		);
+	}
+
+	compareAncestorCurrent(editor: vscode.TextEditor, conflict: interfaces.IDocumentMergeConflict | null) {
+		return this.compare(
+			editor,
+			conflict,
+			vscode.l10n.t("Common Ancestor"),
+			// Fall back to not showing any changes if there's no common ancestor.
+			// This can happen if the conflict file is broken, or they use the
+			// command palette to run this command on a file without common
+			// ancestors markers.
+			(conflict: interfaces.IDocumentMergeConflict) => conflict.commonAncestors[0] || conflict.current,
+			vscode.l10n.t("Current Changes"),
+			(conflict: interfaces.IDocumentMergeConflict) => conflict.current,
+		);
+	}
+
+	compareAncestorIncoming(editor: vscode.TextEditor, conflict: interfaces.IDocumentMergeConflict | null) {
+		return this.compare(
+			editor,
+			conflict,
+			vscode.l10n.t("Common Ancestor"),
+			// Fall back to not showing any changes if there's no common ancestor.
+			// This can happen if the conflict file is broken, or they use the
+			// command palette to run this command on a file without common
+			// ancestors markers.
+			(conflict: interfaces.IDocumentMergeConflict) => conflict.commonAncestors[0] || conflict.incoming,
+			vscode.l10n.t("Incoming Changes"),
+			(conflict: interfaces.IDocumentMergeConflict) => conflict.incoming,
+		);
+	}
+
 	navigateNext(editor: vscode.TextEditor): Promise<void> {
 		return this.navigate(editor, NavigationDirection.Forwards);
 	}