Git: track the repositories containing each commit (#884)

This modifies the Git `Repository` data structure so that for every
commit, we track the `RepoId`s of repos containing that commit. This way
we will be able to do things like hyperlink to the right url for that
commit.

`loadRepository` has been modified to set the initial `repoId`.
`mergeRepository` has been updated to ensure that it concatenates the
`repoId`s properly.
Tests were added for both cases.

The example-git snapshot has been updated accordingly.

Test plan: `yarn test --full`

src/plugins/git/cloneAndLoadRepository.js

@@ -20,7 +20,7 @@ export default function cloneAndLoadRepository(repoId: RepoId): Repository {
   const tmpdir = tmp.dirSync({unsafeCleanup: true});
   const git = localGit(tmpdir.name);
   git(["clone", cloneUrl, ".", "--quiet"]);
-  const result = loadRepository(tmpdir.name, "HEAD");
+  const result = loadRepository(tmpdir.name, "HEAD", repoId);
   tmpdir.removeCallback();
   return result;
 }

src/plugins/git/example/example-git.json

@@ -1,4 +1,30 @@
 {
+    "commitToRepoId": {
+        "3715ddfb8d4c4fd2a6f6af75488c82f84c92ec2f": {
+            "sourcecred/example-git": true
+        },
+        "69c5aad50eec8f2a0a07c988c3b283a6490eb45b": {
+            "sourcecred/example-git": true
+        },
+        "8d287c3bfbf8455ef30187bf5153ffc1b6eef268": {
+            "sourcecred/example-git": true
+        },
+        "c08ee3a4edea384d5291ffcbf06724a13ed72325": {
+            "sourcecred/example-git": true
+        },
+        "c2b51945e7457546912a8ce158ed9d294558d294": {
+            "sourcecred/example-git": true
+        },
+        "c90f6424017f787bbbaf22e4082a01355546f7e3": {
+            "sourcecred/example-git": true
+        },
+        "d160cca97611e9dfed642522ad44408d0292e8ea": {
+            "sourcecred/example-git": true
+        },
+        "e8b7a8f19701cd5a25e4a097d513ead60e5f8bcc": {
+            "sourcecred/example-git": true
+        }
+    },
     "commits": {
         "3715ddfb8d4c4fd2a6f6af75488c82f84c92ec2f": {
             "hash": "3715ddfb8d4c4fd2a6f6af75488c82f84c92ec2f",

src/plugins/git/loadRepository.js

@@ -9,9 +9,15 @@
  */
 // @flow
 
+import * as MapUtil from "../../util/map";
 import type {GitDriver} from "./gitUtils";
-import type {Repository, Hash, Commit} from "./types";
+import type {Repository, Commit} from "./types";
 import {localGit} from "./gitUtils";
+import {
+  repoIdToString,
+  type RepoId,
+  type RepoIdString,
+} from "../../core/repoId";
 
 /**
  * Load a Git repository from disk into memory. The `rootRef` should be
@@ -21,7 +27,8 @@ import {localGit} from "./gitUtils";
  */
 export function loadRepository(
   repositoryPath: string,
-  rootRef: string
+  rootRef: string,
+  repoId: RepoId
 ): Repository {
   const git = localGit(repositoryPath);
   try {
@@ -32,18 +39,18 @@ export function loadRepository(
     git(["rev-parse", "--verify", "HEAD"]);
   } catch (e) {
     // No data in the repository.
-    return {commits: {}};
+    return {commits: {}, commitToRepoId: {}};
   }
-  const commits = findCommits(git, rootRef);
-  return {commits: objectMap(commits)};
-}
-
-function objectMap<T: {+hash: Hash}>(ts: $ReadOnlyArray<T>): {[Hash]: T} {
-  const result = {};
-  ts.forEach((t) => {
-    result[t.hash] = t;
+  const rawCommits = findCommits(git, rootRef);
+  const commits = MapUtil.toObject(new Map(rawCommits.map((x) => [x.hash, x])));
+  const repoIdString = repoIdToString(repoId);
+  const repoIdStringSet: () => {[RepoIdString]: true} = () => ({
+    [((repoIdString: RepoIdString): any)]: true,
   });
-  return result;
+  const commitToRepoId = MapUtil.toObject(
+    new Map(rawCommits.map(({hash}) => [hash, repoIdStringSet()]))
+  );
+  return {commits, commitToRepoId};
 }
 
 function findCommits(git: GitDriver, rootRef: string): Commit[] {

src/plugins/git/loadRepository.test.js

@@ -2,6 +2,7 @@
 
 import tmp from "tmp";
 
+import {makeRepoId, repoIdToString} from "../../core/repoId";
 import {createExampleRepo} from "./example/exampleRepo";
 import {localGit} from "./gitUtils";
 import {loadRepository} from "./loadRepository";
@@ -25,15 +26,38 @@ describe("plugins/git/loadRepository", () => {
     // In case of failure, run
     //     src/plugins/git/loadRepositoryTest.sh --updateSnapshot
     // to update the snapshot, then inspect the resulting changes.
-    expect(loadRepository(repository.path, "HEAD")).toEqual(
-      require("./example/example-git.json")
-    );
+    expect(
+      loadRepository(
+        repository.path,
+        "HEAD",
+        makeRepoId("sourcecred", "example-git")
+      )
+    ).toEqual(require("./example/example-git.json"));
+  });
+
+  it("sets the right repoId for every commit", () => {
+    const gitRepository = createExampleRepo(mkdtemp());
+    const repoId = makeRepoId("sourcecred", "example-git");
+    const repository = loadRepository(gitRepository.path, "HEAD", repoId);
+    for (const commitHash of Object.keys(repository.commits)) {
+      expect(Object.keys(repository.commitToRepoId[commitHash])).toEqual([
+        repoIdToString(repoId),
+      ]);
+    }
   });
 
   it("processes an old commit", () => {
     const repository = createExampleRepo(mkdtemp());
-    const whole = loadRepository(repository.path, "HEAD");
-    const part = loadRepository(repository.path, repository.commits[1]);
+    const whole = loadRepository(
+      repository.path,
+      "HEAD",
+      makeRepoId("sourcecred", "example-git")
+    );
+    const part = loadRepository(
+      repository.path,
+      repository.commits[1],
+      makeRepoId("sourcecred", "example-git")
+    );
 
     // Check that `part` is a subset of `whole`...
     Object.keys(part.commits).forEach((hash) => {
@@ -50,7 +74,11 @@ describe("plugins/git/loadRepository", () => {
     const repository = createExampleRepo(mkdtemp());
     const invalidHash = "0".repeat(40);
     expect(() => {
-      loadRepository(repository.path, invalidHash);
+      loadRepository(
+        repository.path,
+        invalidHash,
+        makeRepoId("sourcecred", "example-git")
+      );
     }).toThrow("fatal: bad object 0000000000000000000000000000000000000000");
   });
 
@@ -58,8 +86,15 @@ describe("plugins/git/loadRepository", () => {
     const repositoryPath = mkdtemp();
     const git = localGit(repositoryPath);
     git(["init"]);
-    expect(loadRepository(repositoryPath, "HEAD")).toEqual({
+    expect(
+      loadRepository(
+        repositoryPath,
+        "HEAD",
+        makeRepoId("sourcecred", "example-git")
+      )
+    ).toEqual({
       commits: {},
+      commitToRepoId: {},
     });
   });
 });

src/plugins/git/mergeRepository.js

@@ -6,18 +6,23 @@ import type {Repository} from "./types";
 export function mergeRepository(
   repositories: $ReadOnlyArray<Repository>
 ): Repository {
-  const newRepository = {commits: {}};
-  for (const {commits} of repositories) {
+  const newCommits = {};
+  const newCommitToRepoId = {};
+  for (const {commits, commitToRepoId} of repositories) {
     for (const commitHash of Object.keys(commits)) {
-      const existingCommit = newRepository.commits[commitHash];
+      const existingCommit = newCommits[commitHash];
       if (
         existingCommit != null &&
         !deepEqual(existingCommit, commits[commitHash])
       ) {
         throw new Error(`Conflict between commits at ${commitHash}`);
       }
-      newRepository.commits[commitHash] = commits[commitHash];
+      newCommits[commitHash] = commits[commitHash];
+      const newRepos = commitToRepoId[commitHash];
+      const existingRepos = newCommitToRepoId[commitHash] || {};
+      const combinedRepoIdsForCommit = {...newRepos, ...existingRepos};
+      newCommitToRepoId[commitHash] = combinedRepoIdsForCommit;
     }
   }
-  return newRepository;
+  return {commits: newCommits, commitToRepoId: newCommitToRepoId};
 }

src/plugins/git/mergeRepository.test.js

@@ -1,11 +1,14 @@
 //@flow
 
+import {makeRepoId, repoIdToString, type RepoIdString} from "../../core/repoId";
 import type {Repository} from "./types";
 import {mergeRepository} from "./mergeRepository";
 
 describe("plugins/git/mergeRepository", () => {
   describe("mergeRepository", () => {
-    const empty: Repository = Object.freeze({commits: {}});
+    const empty: Repository = Object.freeze({commits: {}, commitToRepoId: {}});
+    const repoId1 = repoIdToString(makeRepoId("repo", "1"));
+    const repoId2 = repoIdToString(makeRepoId("repo", "2"));
     const repository1: Repository = Object.freeze({
       commits: {
         commit1: {
@@ -21,6 +24,10 @@ describe("plugins/git/mergeRepository", () => {
           parentHashes: ["commit1"],
         },
       },
+      commitToRepoId: {
+        commit1: {[((repoId1: RepoIdString): any)]: true},
+        commit2: {[((repoId1: RepoIdString): any)]: true},
+      },
     });
     const repository2: Repository = Object.freeze({
       commits: {
@@ -37,6 +44,10 @@ describe("plugins/git/mergeRepository", () => {
           parentHashes: ["commit1"],
         },
       },
+      commitToRepoId: {
+        commit1: {[((repoId2: RepoIdString): any)]: true},
+        commit3: {[((repoId2: RepoIdString): any)]: true},
+      },
     });
 
     it("returns empty repository with no arguments", () => {
@@ -59,6 +70,20 @@ describe("plugins/git/mergeRepository", () => {
         }
       }
     });
+    it("commitToRepoId tracks every repository containing each commit", () => {
+      const merged = mergeRepository([repository1, repository2]);
+      expect(merged.commitToRepoId).toEqual({
+        commit1: {
+          [((repoId2: RepoIdString): any)]: true,
+          [((repoId1: RepoIdString): any)]: true,
+        },
+        commit2: {[((repoId1: RepoIdString): any)]: true},
+        commit3: {[((repoId2: RepoIdString): any)]: true},
+      });
+    });
+    it("merging a repo with itself returns that repo", () => {
+      expect(mergeRepository([repository1, repository1])).toEqual(repository1);
+    });
     it("throws an error if merging a repository with conflicting commits", () => {
       const conflictingRepository: Repository = Object.freeze({
         commits: {
@@ -69,6 +94,11 @@ describe("plugins/git/mergeRepository", () => {
             parentHashes: ["commit0"],
           },
         },
+        commitToRepoId: {
+          commit1: {
+            [((repoId1: RepoIdString): any)]: true,
+          },
+        },
       });
       expect(() =>
         mergeRepository([repository1, conflictingRepository])

src/plugins/git/render.test.js

@@ -1,5 +1,6 @@
 // @flow
 
+import {makeRepoId} from "../../core/repoId";
 import * as GN from "./nodes";
 import {description} from "./render";
 import type {Repository} from "./types";
@@ -19,6 +20,9 @@ describe("plugins/git/render", () => {
         parentHashes: [],
       },
     },
+    commitToRepoId: {
+      [exampleHash]: {[(makeRepoId("sourcecred", "example-git"): any)]: true},
+    },
   });
 
   it("commit snapshots as expected", () => {

src/plugins/git/types.js

@@ -1,7 +1,12 @@
 // @flow
 
+import type {RepoIdString} from "../../core/repoId";
+
 export type Repository = {|
   +commits: {[Hash]: Commit},
+  // For every commit, track all the RepoIds of repos
+  // containing this commit.
+  +commitToRepoId: {[Hash]: {+[RepoIdString]: true}},
 |};
 export type Hash = string;
 export type Commit = {|