Implement defaultBranch()

lahmatiy · lahmatiy · commit c61846b05354 · 2022-09-12T21:14:21.000+02:00
diff --git a/README.md b/README.md
@@ -44,6 +44,24 @@ Common parameters:
 - `ref`: string – a reference to an object in repository
 - `withOid`: boolean – a flag to include resolved oid for a reference
 
+#### repo.defaultBranch()
+
+Returns default branch name used in a repo:
+
+```js
+const defaultBranch = await repo.defaultBranch();
+// 'main'
+```
+
+The algorithm to identify a default branch name:
+
+- if there is only one branch, that must be the default
+- otherwise looking for specific branch names, in this order:
+  - `upstream/HEAD`
+  - `origin/HEAD`
+  - `main`
+  - `master`
+
 #### repo.expandRef(ref)
 
 Expands a `ref` into a full form, e.g. `'main'` -> `'refs/heads/main'`.
diff --git a/fixtures/clean/_git/HEAD b/fixtures/clean/_git/HEAD
@@ -0,0 +1 @@
+ref: refs/heads/development
diff --git a/fixtures/clean/_git/config b/fixtures/clean/_git/config
@@ -0,0 +1,7 @@
+[core]
+	repositoryformatversion = 0
+	filemode = true
+	bare = false
+	logallrefupdates = true
+	ignorecase = true
+	precomposeunicode = true
diff --git a/fixtures/clean/_git/description b/fixtures/clean/_git/description
@@ -0,0 +1 @@
+Unnamed repository; edit this file 'description' to name the repository.
diff --git a/fixtures/clean/_git/info/exclude b/fixtures/clean/_git/info/exclude
@@ -0,0 +1,6 @@
+# git ls-files --others --exclude-from=.git/info/exclude
+# Lines that start with '#' are comments.
+# For a project mostly in C, the following would be a good set of
+# exclude patterns (uncomment them if you want to use them):
+# *.[oa]
+# *~
diff --git a/fixtures/clean/data.json b/fixtures/clean/data.json
@@ -0,0 +1 @@
+{}
diff --git a/fixtures/no-remotes/_git/HEAD b/fixtures/no-remotes/_git/HEAD
@@ -0,0 +1 @@
+ref: refs/heads/main
diff --git a/fixtures/no-remotes/_git/config b/fixtures/no-remotes/_git/config
@@ -0,0 +1,13 @@
+[core]
+	repositoryformatversion = 0
+	filemode = true
+	bare = false
+	logallrefupdates = true
+	ignorecase = true
+	precomposeunicode = true
+[remote "origin"]
+	url = /scan-git/
+	fetch = +refs/heads/*:refs/remotes/origin/*
+[branch "main"]
+	remote = origin
+	merge = refs/heads/main
diff --git a/fixtures/no-remotes/_git/index b/fixtures/no-remotes/_git/index
diff --git a/fixtures/no-remotes/_git/info/refs b/fixtures/no-remotes/_git/info/refs
@@ -0,0 +1 @@
+7b84f676f2fbea2a3c6d83924fa63059c7bdfbe2	refs/heads/main
diff --git a/fixtures/no-remotes/_git/objects/info/packs b/fixtures/no-remotes/_git/objects/info/packs
@@ -0,0 +1,2 @@
+P pack-f3362f24bf3bc5d832ab6197813d07214cb29898.pack
+
diff --git a/fixtures/no-remotes/_git/objects/pack/pack-f3362f24bf3bc5d832ab6197813d07214cb29898.idx b/fixtures/no-remotes/_git/objects/pack/pack-f3362f24bf3bc5d832ab6197813d07214cb29898.idx
diff --git a/fixtures/no-remotes/_git/objects/pack/pack-f3362f24bf3bc5d832ab6197813d07214cb29898.pack b/fixtures/no-remotes/_git/objects/pack/pack-f3362f24bf3bc5d832ab6197813d07214cb29898.pack
diff --git a/fixtures/no-remotes/_git/packed-refs b/fixtures/no-remotes/_git/packed-refs
@@ -0,0 +1,2 @@
+# pack-refs with: peeled fully-peeled sorted 
+7b84f676f2fbea2a3c6d83924fa63059c7bdfbe2 refs/heads/main
diff --git a/fixtures/no-remotes/_git/refs/heads/main b/fixtures/no-remotes/_git/refs/heads/main
@@ -0,0 +1 @@
+293e1ffaf7158c249fc654aec07eca555a25de09
diff --git a/fixtures/no-remotes/_git/refs/heads/test b/fixtures/no-remotes/_git/refs/heads/test
@@ -0,0 +1 @@
+293e1ffaf7158c249fc654aec07eca555a25de09
diff --git a/fixtures/no-remotes/data.json b/fixtures/no-remotes/data.json
@@ -0,0 +1 @@
+{}
diff --git a/fixtures/upstream/_git/FETCH_HEAD b/fixtures/upstream/_git/FETCH_HEAD
@@ -0,0 +1,2 @@
+293e1ffaf7158c249fc654aec07eca555a25de09	not-for-merge	branch 'main' of https://github.com/discoveryjs/scan-git
+6915464f732b3b8652426d1b80d4bcfc6586b176	not-for-merge	branch 'win' of https://github.com/discoveryjs/scan-git
diff --git a/fixtures/upstream/_git/HEAD b/fixtures/upstream/_git/HEAD
@@ -0,0 +1 @@
+ref: refs/heads/fork-main
diff --git a/fixtures/upstream/_git/config b/fixtures/upstream/_git/config
@@ -0,0 +1,16 @@
+[core]
+	repositoryformatversion = 0
+	filemode = true
+	bare = false
+	logallrefupdates = true
+	ignorecase = true
+	precomposeunicode = true
+[remote "origin"]
+	url = https://github.com/lahmatiy/scan-git
+	fetch = +refs/heads/*:refs/remotes/origin/*
+[branch "fork-main"]
+	remote = origin
+	merge = refs/heads/fork-main
+[remote "upstream"]
+	url = https://github.com/discoveryjs/scan-git
+	fetch = +refs/heads/*:refs/remotes/upstream/*
diff --git a/fixtures/upstream/_git/index b/fixtures/upstream/_git/index
diff --git a/fixtures/upstream/_git/info/exclude b/fixtures/upstream/_git/info/exclude
@@ -0,0 +1,6 @@
+# git ls-files --others --exclude-from=.git/info/exclude
+# Lines that start with '#' are comments.
+# For a project mostly in C, the following would be a good set of
+# exclude patterns (uncomment them if you want to use them):
+# *.[oa]
+# *~
diff --git a/fixtures/upstream/_git/objects/pack/pack-4443fbb276799e58fe8e5844969c8900d2e3b27a.idx b/fixtures/upstream/_git/objects/pack/pack-4443fbb276799e58fe8e5844969c8900d2e3b27a.idx
diff --git a/fixtures/upstream/_git/objects/pack/pack-4443fbb276799e58fe8e5844969c8900d2e3b27a.pack b/fixtures/upstream/_git/objects/pack/pack-4443fbb276799e58fe8e5844969c8900d2e3b27a.pack
diff --git a/fixtures/upstream/_git/packed-refs b/fixtures/upstream/_git/packed-refs
@@ -0,0 +1,2 @@
+# pack-refs with: peeled fully-peeled sorted 
+293e1ffaf7158c249fc654aec07eca555a25de09 refs/remotes/origin/main
diff --git a/fixtures/upstream/_git/refs/heads/fork-main b/fixtures/upstream/_git/refs/heads/fork-main
@@ -0,0 +1 @@
+293e1ffaf7158c249fc654aec07eca555a25de09
diff --git a/fixtures/upstream/_git/refs/remotes/origin/HEAD b/fixtures/upstream/_git/refs/remotes/origin/HEAD
@@ -0,0 +1 @@
+ref: refs/remotes/origin/fork-main
diff --git a/fixtures/upstream/_git/refs/remotes/origin/fork-main b/fixtures/upstream/_git/refs/remotes/origin/fork-main
@@ -0,0 +1 @@
+293e1ffaf7158c249fc654aec07eca555a25de09
diff --git a/fixtures/upstream/_git/refs/remotes/upstream/main b/fixtures/upstream/_git/refs/remotes/upstream/main
@@ -0,0 +1 @@
+293e1ffaf7158c249fc654aec07eca555a25de09
diff --git a/fixtures/upstream/_git/refs/remotes/upstream/win b/fixtures/upstream/_git/refs/remotes/upstream/win
@@ -0,0 +1 @@
+6915464f732b3b8652426d1b80d4bcfc6586b176
diff --git a/fixtures/upstream/data.json b/fixtures/upstream/data.json
@@ -0,0 +1 @@
+{}
diff --git a/src/resolve-ref.ts b/src/resolve-ref.ts
@@ -1,5 +1,5 @@
 import { promises as fsPromises, existsSync } from 'fs';
-import { join as pathJoin, sep as pathSep } from 'path';
+import { join as pathJoin, basename, sep as pathSep } from 'path';
 import { scanFs } from '@discoveryjs/scan-fs';
 
 type Ref = { name: string; oid: string };
@@ -98,6 +98,12 @@ export async function createRefIndex(gitdir: string) {
         listRefs(`refs/remotes/${remote}/`, withOids);
     const listBranches = (withOids = false) => listRefs('refs/heads/', withOids);
     const listTags = (withOids = false) => listRefs('refs/tags/', withOids);
+    const readRefContent = async (ref: string) =>
+        basename(
+            (await fsPromises.readFile(pathJoin(gitdir, ref), 'utf8'))
+                .trim()
+                .replace(/^ref:\s*/, '')
+        );
 
     return {
         resolveRef,
@@ -113,6 +119,29 @@ export async function createRefIndex(gitdir: string) {
         listBranches,
         listTags,
 
+        // inspired by https://usethis.r-lib.org/reference/git-default-branch.html
+        async defaultBranch() {
+            const branches = (await listBranches()) as string[]; // FIXME: remove string[]
+
+            if (branches.length === 1) {
+                return basename(branches[0]);
+            }
+
+            const branchRef =
+                expandRef('refs/remotes/upstream/HEAD') ||
+                expandRef('refs/remotes/origin/HEAD') ||
+                expandRef('refs/heads/main') ||
+                expandRef('refs/heads/master');
+
+            if (branchRef) {
+                return branchRef.endsWith('/HEAD')
+                    ? readRefContent(branchRef)
+                    : basename(branchRef);
+            }
+
+            return null;
+        },
+
         async stat() {
             const remotes = listRemotes();
             const branchesByRemote = await Promise.all(
diff --git a/test/helpers/fixture.ts b/test/helpers/fixture.ts
@@ -2,19 +2,23 @@ import fs from 'fs';
 import { fileURLToPath } from 'url';
 import { createGitReader, GitReaderOptions } from '@discoveryjs/scan-git';
 
-const fixturesConfig = {
-    base: '../../fixtures/base',
-    cruft: '../../fixtures/cruft'
-};
+const fixturesPath = '../../fixtures/';
+const fixtureNames = ['base', 'cruft', 'no-remotes', 'upstream', 'clean'];
 
 export const fixtures = Object.create(null);
 
-for (const [name, path] of Object.entries(fixturesConfig)) {
+for (const name of fixtureNames) {
     fixtures[name] = {
         repo: (options?: GitReaderOptions) =>
-            createGitReader(fileURLToPath(new URL(path + '/_git', import.meta.url)), options),
+            createGitReader(
+                fileURLToPath(new URL(fixturesPath + name + '/_git', import.meta.url)),
+                options
+            ),
         data: JSON.parse(
-            fs.readFileSync(fileURLToPath(new URL(path + '/data.json', import.meta.url)), 'utf8')
+            fs.readFileSync(
+                fileURLToPath(new URL(fixturesPath + name + '/data.json', import.meta.url)),
+                'utf8'
+            )
         )
     };
 }
diff --git a/test/resolve-ref.ts b/test/resolve-ref.ts
@@ -13,6 +13,27 @@ describe('resolve-ref', () => {
     before(async () => (repo = await fixtures.base.repo()));
     after(() => repo.dispose().then(() => (repo = null)));
 
+    describe('defaultBranch()', () => {
+        const defaultBranches = {
+            base: 'main',
+            cruft: 'main',
+            'no-remotes': 'main',
+            upstream: 'fork-main',
+            clean: 'development' // FIXME
+        };
+
+        for (const [repoName, expected] of Object.entries(defaultBranches)) {
+            (repoName === 'clean' ? it.skip : it)(repoName, async () => {
+                const repo = await fixtures[repoName].repo();
+                const actual = await repo.defaultBranch();
+
+                assert.strictEqual(actual, expected);
+
+                return repo.dispose();
+            });
+        }
+    });
+
     describe('listBranches()', () => {
         it('local branches', async () => {
             const actual = await repo.listBranches();
@@ -59,7 +80,9 @@ describe('resolve-ref', () => {
 
             assert.deepStrictEqual(actual, expected);
         });
+    });
 
+    describe('listRemoteBranches()', () => {
         it('remote branches', async () => {
             const actual = await repo.listRemoteBranches('origin');
             const expected = [

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1 @@`
	`1`	`+Unnamed repository; edit this file 'description' to name the repository.`
Original file line number	Diff line number	Diff line change
`@@ -0,0 +1 @@`
	`1`	`+7b84f676f2fbea2a3c6d83924fa63059c7bdfbe2 refs/heads/main`