Use direct force pushes by committing first to a temp branch (#70)

* Switch to using REST API for branch upserts

* Rollback to using graphql

* Use a temp branch strategy

* add tests

* fix lint

* fmt

* fix graphql usage

* add changeset

* Apply suggestion from @Andarist

Author: Andarist

.changeset/friendly-rivers-protect.md

@@ -0,0 +1,5 @@
+---
+"@changesets/ghcommit": minor
+---
+
+Improve force-push handling so updating an existing branch no longer temporarily resets the target branch to the base commit, avoiding cases where GitHub closes open pull requests during the update.

src/core.ts

@@ -1,13 +1,8 @@
 import {
   createCommitOnBranchQuery,
-  createRefMutation,
   getRepositoryMetadata,
-  updateRefMutation,
 } from "./github/graphql/queries.js";
-import type {
-  CreateCommitOnBranchMutationVariables,
-  GetRepositoryMetadataQuery,
-} from "./github/graphql/generated/operations.js";
+import type { GetRepositoryMetadataQuery } from "./github/graphql/generated/operations.js";
 import {
   CommitFilesFromBase64Args,
   CommitFilesResult,
@@ -21,6 +16,8 @@ const getBaseRef = (base: GitBase): string => {
   } else if ("tag" in base) {
     return `refs/tags/${base.tag}`;
   } else {
+    // For explicit commit bases we don't resolve the base oid from a ref,
+    // but the shared metadata query still expects a valid qualified ref name.
     return "HEAD";
   }
 };
@@ -45,6 +42,47 @@ const getOidFromRef = (
   return ref.target.oid;
 };
 
+const isAlreadyExistingRefError = (error: unknown) =>
+  typeof error === "object" &&
+  error !== null &&
+  "status" in error &&
+  "message" in error &&
+  typeof error.status === "number" &&
+  typeof error.message === "string" &&
+  error.status === 422 &&
+  error.message.includes("Reference already exists");
+
+const createCommit = async ({
+  octokit,
+  refId,
+  baseOid,
+  message,
+  fileChanges,
+}: Pick<CommitFilesFromBase64Args, "octokit" | "message" | "fileChanges"> & {
+  refId: string;
+  baseOid: string;
+}) => {
+  const normalizedMessage: CommitMessage =
+    typeof message === "string"
+      ? {
+          headline: message.split("\n")[0]?.trim() ?? "",
+          body: message.split("\n").slice(1).join("\n").trim(),
+        }
+      : message;
+
+  // we have to stick to GraphQL here as with REST, each file change would become a separate API call
+  return createCommitOnBranchQuery(octokit, {
+    input: {
+      branch: {
+        id: refId,
+      },
+      expectedHeadOid: baseOid,
+      message: normalizedMessage,
+      fileChanges,
+    },
+  });
+};
+
 export const commitFilesFromBase64 = async ({
   octokit,
   owner,
@@ -70,115 +108,160 @@ export const commitFilesFromBase64 = async ({
   log?.debug(`Repo info: ${JSON.stringify(info, null, 2)}`);
 
   if (!info) {
-    throw new Error(`Repository ${repositoryNameWithOwner} not found`);
+    throw new Error(
+      `Repository ${JSON.stringify(repositoryNameWithOwner)} not found`,
+    );
+  }
+  if (!("commit" in base) && !info.baseRef) {
+    throw new Error(`Ref ${JSON.stringify(baseRef)} not found`);
   }
 
-  const repositoryId = info.id;
+  const resolvedBaseRef = info.baseRef;
+
   /**
    * The commit oid to base the new commit on.
    *
-   * Used both to create / update the new branch (if necessary),
-   * and to ensure no changes have been made as we push the new commit.
+   * Used both to create the new commit,
+   * and to determine whether an existing branch can be updated.
    */
   const baseOid = getOidFromRef(base, info.baseRef);
+  const targetOid = info.targetBranch?.target?.oid ?? null;
+  const sameBranchBase = "branch" in base && base.branch === branch;
 
-  let refId: string;
-
-  if ("branch" in base && base.branch === branch) {
-    log?.debug(`Committing to the same branch as base: ${branch} (${baseOid})`);
-    // Get existing branch refId
+  let mode: "create" | "update" | "force-update";
 
-    if (!info.baseRef) {
-      throw new Error(`Ref ${baseRef} not found`);
-    }
-    refId = info.baseRef.id;
+  if (sameBranchBase) {
+    mode = force ? "force-update" : "update";
+  } else if (targetOid === null) {
+    // TODO: legit *creation* failure should be retried if `force === true`
+    mode = "create";
+  } else if (force) {
+    mode = "force-update";
+  } else if (targetOid === baseOid) {
+    mode = "update";
   } else {
-    // Determine if the branch needs to be created or not
-    if (info.targetBranch?.target?.oid) {
-      // Branch already exists, check if it matches the base
-      if (info.targetBranch.target.oid !== baseOid) {
-        if (force) {
-          log?.debug(
-            `Branch ${branch} exists but does not match base ${baseOid}, forcing update to base`,
-          );
-          const refIdUpdate = await updateRefMutation(octokit, {
-            input: {
-              refId: info.targetBranch.id,
-              oid: baseOid,
-              force: true,
-            },
-          });
-
-          log?.debug(
-            `Updated branch with refId ${JSON.stringify(refIdUpdate, null, 2)}`,
-          );
-
-          const refIdStr = refIdUpdate.updateRef?.ref?.id;
-
-          if (!refIdStr) {
-            throw new Error(`Failed to create branch ${branch}`);
-          }
-
-          refId = refIdStr;
-        } else {
-          throw new Error(
-            `Branch ${branch} exists already and does not match base ${baseOid}, force is set to false`,
-          );
-        }
-      } else {
-        log?.debug(
-          `Branch ${branch} already exists and matches base ${baseOid}`,
-        );
-        refId = info.targetBranch.id;
-      }
-    } else {
-      // Create branch as it does not exist yet
-      log?.debug(`Creating branch ${branch} from commit ${baseOid}}`);
-      const refIdCreation = await createRefMutation(octokit, {
-        input: {
-          repositoryId,
-          name: `refs/heads/${branch}`,
-          oid: baseOid,
-        },
+    throw new Error(
+      `Branch ${branch} exists already and does not match base ${baseOid}, force is set to false`,
+    );
+  }
+
+  if (mode === "force-update") {
+    // Use a stable temp branch name so a later run can recover and reuse it
+    // if an earlier run failed before cleanup completed.
+    const tempBranch = `changesets-ghcommit-temp/${branch}`;
+
+    let tempRefId: string;
+
+    try {
+      const createdTempRef = await octokit.rest.git.createRef({
+        owner,
+        repo,
+        ref: `refs/heads/${tempBranch}`,
+        sha: baseOid,
       });
 
-      log?.debug(
-        `Created branch with refId ${JSON.stringify(refIdCreation, null, 2)}`,
-      );
+      const refIdStr = createdTempRef.data.node_id;
 
-      const refIdStr = refIdCreation.createRef?.ref?.id;
+      if (!refIdStr) {
+        throw new Error(`Failed to create temporary branch ${tempBranch}`);
+      }
+
+      tempRefId = refIdStr;
+    } catch (error) {
+      if (!isAlreadyExistingRefError(error)) {
+        throw error;
+      }
+
+      const updatedTempRef = await octokit.rest.git.updateRef({
+        owner,
+        repo,
+        ref: `heads/${tempBranch}`,
+        sha: baseOid,
+        force: true,
+      });
+
+      const refIdStr = updatedTempRef.data.node_id;
 
       if (!refIdStr) {
-        throw new Error(`Failed to create branch ${branch}`);
+        throw new Error(`Failed to update temporary branch ${tempBranch}`);
       }
 
-      refId = refIdStr;
+      tempRefId = refIdStr;
+    }
+
+    log?.debug(`Creating commit on branch ${tempBranch}`);
+    const tempCommit = await createCommit({
+      octokit,
+      refId: tempRefId,
+      baseOid,
+      message,
+      fileChanges,
+    });
+
+    const tempHeadOid = tempCommit.createCommitOnBranch?.commit?.oid;
+
+    if (!tempHeadOid) {
+      throw new Error(
+        `Failed to determine head commit of temporary branch ${tempBranch}`,
+      );
     }
+
+    const updatedTargetRef = await octokit.rest.git.updateRef({
+      owner,
+      repo,
+      ref: `heads/${branch}`,
+      sha: tempHeadOid,
+      force: true,
+    });
+
+    const updatedTargetRefId = updatedTargetRef.data.node_id;
+
+    if (!updatedTargetRefId) {
+      throw new Error(`Failed to update branch ${branch}`);
+    }
+
+    await octokit.rest.git.deleteRef({
+      owner,
+      repo,
+      ref: `heads/${tempBranch}`,
+    });
+
+    return {
+      refId: updatedTargetRefId,
+    };
   }
 
-  const finalMessage: CommitMessage =
-    typeof message === "string"
-      ? {
-          headline: message.split("\n")[0]?.trim() ?? "",
-          body: message.split("\n").slice(1).join("\n").trim(),
-        }
-      : message;
+  let refId: string;
+
+  if (mode === "create") {
+    const createdRef = await octokit.rest.git.createRef({
+      owner,
+      repo,
+      ref: `refs/heads/${branch}`,
+      sha: baseOid,
+    });
+
+    const refIdStr = createdRef.data.node_id;
+
+    if (!refIdStr) {
+      throw new Error(`Failed to create branch ${branch}`);
+    }
+
+    refId = refIdStr;
+  } else {
+    refId = sameBranchBase ? resolvedBaseRef!.id : info.targetBranch!.id;
+  }
 
   log?.debug(`Creating commit on branch ${branch}`);
-  const createCommitMutation: CreateCommitOnBranchMutationVariables = {
-    input: {
-      branch: {
-        id: refId,
-      },
-      expectedHeadOid: baseOid,
-      message: finalMessage,
-      fileChanges,
-    },
-  };
-  log?.debug(JSON.stringify(createCommitMutation, null, 2));
+  const newCommit = await createCommit({
+    octokit,
+    refId,
+    baseOid,
+    message,
+    fileChanges,
+  });
 
-  const result = await createCommitOnBranchQuery(octokit, createCommitMutation);
   return {
-    refId: result.createCommitOnBranch?.ref?.id ?? null,
+    refId: newCommit.createCommitOnBranch?.ref?.id ?? null,
   };
 };

src/github/graphql/queries.ts

@@ -1,6 +1,6 @@
-export type GitHubClient = {
-  graphql: <T>(query: string, variables: any) => Promise<T>;
-};
+export type GitHubClient = ReturnType<
+  typeof import("@actions/github").getOctokit
+>;
 
 import type {
   CreateCommitOnBranchMutation,
@@ -78,6 +78,9 @@ const DELETE_REF = /* GraphQL */ `
 const CREATE_COMMIT_ON_BRANCH = /* GraphQL */ `
   mutation createCommitOnBranch($input: CreateCommitOnBranchInput!) {
     createCommitOnBranch(input: $input) {
+      commit {
+        oid
+      }
       ref {
         id
       }