diff --git a/apps/cli/src/index.tsx b/apps/cli/src/index.tsx
index 540347b..f40a4c5 100644
--- a/apps/cli/src/index.tsx
+++ b/apps/cli/src/index.tsx
@@ -41,7 +41,10 @@ const command = program
     3000,
   )
   .option("-n, --no-upgrade", "skip applying the upgrade")
-  .option("-a, --auto-detect", "auto-detect the package to upgrade")
+  .option(
+    "-a, --auto-detect [branch]",
+    "auto-detect the package to upgrade, diff against [branch]",
+  )
   .option("-s, --simple", "simple mode")
   .option("-i, --ipc", "run in ipc mode")
   .option("-d, --dir <dir>", "target directory for the upgrade")
diff --git a/packages/bumpgen-core/src/index.ts b/packages/bumpgen-core/src/index.ts
index 1506212..02e3dae 100644
--- a/packages/bumpgen-core/src/index.ts
+++ b/packages/bumpgen-core/src/index.ts
@@ -67,10 +67,10 @@ const bumpFinder = ({
       const { projectRoot } = args;
       return await language.packages.upgrade.list(projectRoot);
     },
-    detect: async () => {
+    detect: async (target?: string) => {
       const { language } = services;
       const { projectRoot } = args;
-      return await language.packages.upgrade.detect(projectRoot);
+      return await language.packages.upgrade.detect(projectRoot, target);
     },
   };
 };
diff --git a/packages/bumpgen-core/src/services/language/types.ts b/packages/bumpgen-core/src/services/language/types.ts
index d740fde..59ec74a 100644
--- a/packages/bumpgen-core/src/services/language/types.ts
+++ b/packages/bumpgen-core/src/services/language/types.ts
@@ -20,7 +20,10 @@ export type BumpgenLanguageService<TAst = any> = {
   packages: {
     upgrade: {
       list: (projectRoot: string) => Promise<PackageUpgrade[]>;
-      detect: (projectRoot: string) => Promise<PackageUpgrade[]>;
+      detect: (
+        projectRoot: string,
+        target?: string,
+      ) => Promise<PackageUpgrade[]>;
       apply: (
         projectRoot: string,
         upgrade: PackageUpgrade,
diff --git a/packages/bumpgen-core/src/services/language/typescript/index.ts b/packages/bumpgen-core/src/services/language/typescript/index.ts
index 9f1f520..8cc53b0 100644
--- a/packages/bumpgen-core/src/services/language/typescript/index.ts
+++ b/packages/bumpgen-core/src/services/language/typescript/index.ts
@@ -211,7 +211,7 @@ export const makeTypescriptService = (
             };
           });
         },
-        detect: async (projectRoot) => {
+        detect: async (projectRoot, target) => {
           const packageJson = await PackageJson.load(projectRoot);
 
           const existingDependencies = new Set([
@@ -224,15 +224,9 @@ export const makeTypescriptService = (
           ]);
 
           await git.raw.cwd(projectRoot);
-          const branch = (await git.raw.branch()).current;
+          const branch = target ?? (await git.raw.branch()).current;
 
-          let diff = await git.raw.diff([branch, "package.json"]);
-
-          // if there are no changes in the package.json, we check against the main branch
-          if (!diff) {
-            const mainBranch = await git.getMainBranch(projectRoot);
-            diff = await git.raw.diff([mainBranch, "package.json"]);
-          }
+          const diff = await git.raw.diff([branch, "package.json"]);
 
           const upgradedPackages = [];