Check that git branch is up to date before publishing

1 files changed, 17 insertions, 1 deletions

diff --git a/packages/monorepo-scripts/src/prepublish_checks.ts b/packages/monorepo-scripts/src/prepublish_checks.ts
index ae58524f5..2c096d8f6 100644
--- a/packages/monorepo-scripts/src/prepublish_checks.ts
+++ b/packages/monorepo-scripts/src/prepublish_checks.ts
@@ -47,9 +47,25 @@ async function checkPublishRequiredSetupAsync(): Promise<void> {
     } catch (err) {
         throw new Error('You must setup your AWS credentials by running `aws configure`. Do this and try again.');
     }
+
+    utils.log('Checking that git branch is up to date with upstream...');
+    await execAsync('git fetch');
+    const res = await execAsync('git status -bs'); // s - short format, b - branch info
+    /**
+     * Possible outcomes
+     * ## branch_name...origin/branch_name [behind n]
+     * ## branch_name...origin/branch_name [ahead n]
+     * ## branch_name...origin/branch_name
+     */
+    const gitShortStatusHeader = res.stdout.split('\n')[0];
+    if (gitShortStatusHeader.includes('behind')) {
+        throw new Error('Your branch is behind upstream. Please pull before publishing.');
+    } else if (gitShortStatusHeader.includes('ahead')) {
+        throw new Error('Your branch is ahead of upstream. Please push before publishing.');
+    }
 }
 
 checkPublishRequiredSetupAsync().catch(err => {
-    utils.log(err);
+    utils.log(err.message);
     process.exit(1);
 });