From 3fff78b18aa9f125868f831b4ab5ab26c13de402 Mon Sep 17 00:00:00 2001
From: Ladislau Szomoru <3372902+lszomoru@users.noreply.github.com>
Date: Mon, 27 Oct 2025 23:37:10 +0100
Subject: [PATCH] Graph - add command to compare references (#273635)

---
 extensions/git/package.json     | 15 +++++++++
 extensions/git/package.nls.json |  1 +
 extensions/git/src/commands.ts  | 59 +++++++++++++++++++++++++++++++++
 3 files changed, 75 insertions(+)

diff --git a/extensions/git/package.json b/extensions/git/package.json
index 9ff385ce77f..bc8b9d3d37b 100644
--- a/extensions/git/package.json
+++ b/extensions/git/package.json
@@ -514,6 +514,12 @@
         "category": "Git",
         "enablement": "!operationInProgress"
       },
+      {
+        "command": "git.graph.compareBranches",
+        "title": "%command.graphCompareBranches%",
+        "category": "Git",
+        "enablement": "!operationInProgress"
+      },
       {
         "command": "git.deleteRemoteBranch",
         "title": "%command.deleteRemoteBranch%",
@@ -1594,6 +1600,10 @@
           "command": "git.graph.deleteBranch",
           "when": "false"
         },
+        {
+          "command": "git.graph.compareBranches",
+          "when": "false"
+        },
         {
           "command": "git.graph.deleteTag",
           "when": "false"
@@ -2265,6 +2275,11 @@
           "when": "scmProvider == git && scmHistoryItemRef =~ /^refs\\/heads\\/|^refs\\/remotes\\//",
           "group": "2_branch@2"
         },
+        {
+          "command": "git.graph.compareBranches",
+          "when": "scmProvider == git && scmHistoryItemRef =~ /^refs\\/heads\\//",
+          "group": "2_branch@3"
+        },
         {
           "command": "git.graph.deleteTag",
           "when": "scmProvider == git && scmHistoryItemRef =~ /^refs\\/tags\\//",
diff --git a/extensions/git/package.nls.json b/extensions/git/package.nls.json
index ae4159e566d..dd41ad67f38 100644
--- a/extensions/git/package.nls.json
+++ b/extensions/git/package.nls.json
@@ -135,6 +135,7 @@
 	"command.graphCheckout": "Checkout",
 	"command.graphCheckoutDetached": "Checkout (Detached)",
 	"command.graphCherryPick": "Cherry Pick",
+	"command.graphCompareBranches": "Compare Branches...",
 	"command.graphDeleteBranch": "Delete Branch",
 	"command.graphDeleteTag": "Delete Tag",
 	"command.blameToggleEditorDecoration": "Toggle Git Blame Editor Decoration",
diff --git a/extensions/git/src/commands.ts b/extensions/git/src/commands.ts
index c57ae4606c0..4a59b05ee36 100644
--- a/extensions/git/src/commands.ts
+++ b/extensions/git/src/commands.ts
@@ -3114,6 +3114,65 @@ export class CommandCenter {
 		await this._deleteBranch(repository, undefined, undefined, { remote: true });
 	}
 
+	@command('git.graph.compareBranches', { repository: true })
+	async compareBranches(repository: Repository, historyItem?: SourceControlHistoryItem, historyItemRefId?: string): Promise<void> {
+		const historyItemRef = historyItem?.references?.find(r => r.id === historyItemRefId);
+		if (!historyItemRefId || !historyItemRef) {
+			return;
+		}
+
+		const config = workspace.getConfiguration('git');
+		const showRefDetails = config.get<boolean>('showReferenceDetails') === true;
+
+		const getBranchPicks = async () => {
+			const refs = await repository.getRefs({ includeCommitDetails: showRefDetails });
+			const processors = [
+				new RefProcessor(RefType.Head, BranchItem),
+				new RefProcessor(RefType.Tag, BranchItem)
+			];
+
+			const itemsProcessor = new RefItemsProcessor(repository, processors);
+			return itemsProcessor.processRefs(refs);
+		};
+
+		const placeHolder = l10n.t('Select a source reference to compare to');
+		const sourceRef = await this.pickRef(getBranchPicks(), placeHolder);
+
+		if (!(sourceRef instanceof BranchItem)) {
+			return;
+		}
+
+		if (historyItemRefId === sourceRef.refId) {
+			window.showInformationMessage(l10n.t('The selected references are the same.'));
+			return;
+		}
+
+		try {
+			const changes = await repository.diffTrees(historyItemRefId, sourceRef.refId);
+
+			if (changes.length === 0) {
+				window.showInformationMessage(l10n.t('The selected references have no differences.'));
+				return;
+			}
+
+			const resources = changes.map(change => toMultiFileDiffEditorUris(change, sourceRef.refId, historyItemRefId));
+
+			const title = `${sourceRef.ref.name} ↔ ${historyItemRef.name}`;
+			const multiDiffSourceUri = Uri.from({
+				scheme: 'git-branch-compare',
+				path: `${repository.root}/${sourceRef.refId}..${historyItemRefId}`
+			});
+
+			await commands.executeCommand('_workbench.openMultiDiffEditor', {
+				multiDiffSourceUri,
+				title,
+				resources
+			});
+		} catch (err) {
+			throw new Error(l10n.t('Failed to compare references: {0}', err.message ?? err));
+		}
+	}
+
 	private async _deleteBranch(repository: Repository, remote: string | undefined, name: string | undefined, options: { remote: boolean; force?: boolean }): Promise<void> {
 		let run: (force?: boolean) => Promise<void>;