feat: BASE to undefined if HEAD~1 does not exist (#167)

Author: mandarini

dist/index.js

@@ -37872,6 +37872,7 @@ const defaultWorkingDirectory = '.';
 const ProxifiedClient = action_1.Octokit.plugin(proxyPlugin);
 let BASE_SHA;
 (() => __awaiter(void 0, void 0, void 0, function* () {
+    var _a;
     if (workingDirectory !== defaultWorkingDirectory) {
         if ((0, fs_1.existsSync)(workingDirectory)) {
             process.chdir(workingDirectory);
@@ -37919,17 +37920,27 @@ let BASE_SHA;
                     process.stdout.write(`Using provided fallback SHA: ${fallbackSHA}\n`);
                 }
                 else {
-                    process.stdout.write(`We are therefore defaulting to use HEAD~1 on 'origin/${mainBranchName}'\n`);
-                    process.stdout.write('\n');
-                    process.stdout.write(`NOTE: You can instead make this a hard error by setting 'error-on-no-successful-workflow' on the action in your workflow.\n`);
-                    process.stdout.write('\n');
-                    const commitCountOutput = (0, child_process_1.spawnSync)('git', ['rev-list', '--count', `origin/${mainBranchName}`], { encoding: 'utf-8' }).stdout;
-                    const commitCount = parseInt(stripNewLineEndings(commitCountOutput), 10);
-                    const LAST_COMMIT_CMD = `origin/${mainBranchName}${commitCount > 1 ? '~1' : ''}`;
+                    // Check if HEAD~1 exists, and if not, set BASE_SHA to the empty tree hash
+                    const LAST_COMMIT_CMD = `origin/${mainBranchName}~1`;
                     const baseRes = (0, child_process_1.spawnSync)('git', ['rev-parse', LAST_COMMIT_CMD], {
                         encoding: 'utf-8',
                     });
-                    BASE_SHA = baseRes.stdout;
+                    if (baseRes.status !== 0 || !baseRes.stdout) {
+                        const emptyTreeRes = (0, child_process_1.spawnSync)('git', ['hash-object', '-t', 'tree', '/dev/null'], {
+                            encoding: 'utf-8',
+                        });
+                        // 4b825dc642cb6eb9a060e54bf8d69288fbee4904 is the expected result of hashing the empty tree
+                        BASE_SHA =
+                            (_a = emptyTreeRes.stdout) !== null && _a !== void 0 ? _a : `4b825dc642cb6eb9a060e54bf8d69288fbee4904`;
+                        process.stdout.write(`HEAD~1 does not exist. We are therefore defaulting to use the empty git tree hash as BASE.\n`);
+                    }
+                    else {
+                        process.stdout.write(`We are therefore defaulting to use HEAD~1 on 'origin/${mainBranchName}'\n`);
+                        BASE_SHA = baseRes.stdout;
+                    }
+                    process.stdout.write('\n');
+                    process.stdout.write(`NOTE: You can instead make this a hard error by setting 'error-on-no-successful-workflow' on the action in your workflow.\n`);
+                    process.stdout.write('\n');
                 }
                 core.setOutput('noPreviousBuild', 'true');
             }

find-successful-workflow.ts

@@ -85,32 +85,40 @@ let BASE_SHA: string;
           BASE_SHA = fallbackSHA;
           process.stdout.write(`Using provided fallback SHA: ${fallbackSHA}\n`);
         } else {
-          process.stdout.write(
-            `We are therefore defaulting to use HEAD~1 on 'origin/${mainBranchName}'\n`,
-          );
+          // Check if HEAD~1 exists, and if not, set BASE_SHA to the empty tree hash
+          const LAST_COMMIT_CMD = `origin/${mainBranchName}~1`;
+
+          const baseRes = spawnSync('git', ['rev-parse', LAST_COMMIT_CMD], {
+            encoding: 'utf-8',
+          });
+
+          if (baseRes.status !== 0 || !baseRes.stdout) {
+            const emptyTreeRes = spawnSync(
+              'git',
+              ['hash-object', '-t', 'tree', '/dev/null'],
+              {
+                encoding: 'utf-8',
+              },
+            );
+            // 4b825dc642cb6eb9a060e54bf8d69288fbee4904 is the expected result of hashing the empty tree
+            BASE_SHA =
+              emptyTreeRes.stdout ?? `4b825dc642cb6eb9a060e54bf8d69288fbee4904`;
+            process.stdout.write(
+              `HEAD~1 does not exist. We are therefore defaulting to use the empty git tree hash as BASE.\n`,
+            );
+          } else {
+            process.stdout.write(
+              `We are therefore defaulting to use HEAD~1 on 'origin/${mainBranchName}'\n`,
+            );
+
+            BASE_SHA = baseRes.stdout;
+          }
+
           process.stdout.write('\n');
           process.stdout.write(
             `NOTE: You can instead make this a hard error by setting 'error-on-no-successful-workflow' on the action in your workflow.\n`,
           );
           process.stdout.write('\n');
-
-          const commitCountOutput = spawnSync(
-            'git',
-            ['rev-list', '--count', `origin/${mainBranchName}`],
-            { encoding: 'utf-8' },
-          ).stdout;
-          const commitCount = parseInt(
-            stripNewLineEndings(commitCountOutput),
-            10,
-          );
-
-          const LAST_COMMIT_CMD = `origin/${mainBranchName}${
-            commitCount > 1 ? '~1' : ''
-          }`;
-          const baseRes = spawnSync('git', ['rev-parse', LAST_COMMIT_CMD], {
-            encoding: 'utf-8',
-          });
-          BASE_SHA = baseRes.stdout;
         }
         core.setOutput('noPreviousBuild', 'true');
       }

package.json

@@ -1,6 +1,6 @@
 {
   "private": true,
-  "version": "4.0.6",
+  "version": "4.1.0",
   "license": "MIT",
   "description": "This package.json is here purely to control the version of the Action, in combination with https://github.com/JamesHenry/publish-shell-action",
   "scripts": {