switch to "main" branch for development

We're migrating from "master" to "main" as the default development
branch.  This only affects repo itself, not manifests.

Change-Id: I27489dd721c9a467a1c43736808cb3b3c1365433
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/288082
Reviewed-by: Michael Mortensen <mmortensen@google.com>
Tested-by: Mike Frysinger <vapier@google.com>

.github/workflows/test-ci.yml

@@ -5,7 +5,7 @@ name: Test CI
 
 on:
   push:
-    branches: [master, repo-1, stable, maint]
+    branches: [main, repo-1, stable, maint]
     tags: [v*]
 
 jobs:

SUBMITTING_PATCHES.md

@@ -10,7 +10,7 @@
  - Make corrections if requested.
  - Verify your changes on gerrit so they can be submitted.
 
-   `git push https://gerrit-review.googlesource.com/git-repo HEAD:refs/for/master`
+   `git push https://gerrit-review.googlesource.com/git-repo HEAD:refs/for/main`
 
 
 # Long Version
@@ -150,7 +150,7 @@ Push your patches over HTTPS to the review server, possibly through
 a remembered remote to make this easier in the future:
 
     git config remote.review.url https://gerrit-review.googlesource.com/git-repo
-    git config remote.review.push HEAD:refs/for/master
+    git config remote.review.push HEAD:refs/for/main
 
     git push review
 

docs/internal-fs-layout.md

@@ -106,7 +106,7 @@ support, see the [manifest-format.md] file.
     setting in the manifest (i.e. the path on the remote server) with a `.git`
     suffix.  This allows for multiple checkouts of the same remote git repo to
     share their objects.  For example, you could have different branches of
-    `foo/bar.git` checked out to `foo/bar-master`, `foo/bar-release`, etc...
+    `foo/bar.git` checked out to `foo/bar-main`, `foo/bar-release`, etc...
     There will be multiple trees under `projects/` for each one, but only one
     under `project-objects/`.
 

docs/manifest-format.md

@@ -142,8 +142,8 @@ Attribute `review`: Hostname of the Gerrit server where reviews
 are uploaded to by `repo upload`.  This attribute is optional;
 if not specified then `repo upload` will not function.
 
-Attribute `revision`: Name of a Git branch (e.g. `master` or
-`refs/heads/master`). Remotes with their own revision will override
+Attribute `revision`: Name of a Git branch (e.g. `main` or
+`refs/heads/main`). Remotes with their own revision will override
 the default revision.
 
 ### Element default
@@ -156,11 +156,11 @@ Attribute `remote`: Name of a previously defined remote element.
 Project elements lacking a remote attribute of their own will use
 this remote.
 
-Attribute `revision`: Name of a Git branch (e.g. `master` or
-`refs/heads/master`).  Project elements lacking their own
+Attribute `revision`: Name of a Git branch (e.g. `main` or
+`refs/heads/main`).  Project elements lacking their own
 revision attribute will use this revision.
 
-Attribute `dest-branch`: Name of a Git branch (e.g. `master`).
+Attribute `dest-branch`: Name of a Git branch (e.g. `main`).
 Project elements not setting their own `dest-branch` will inherit
 this value. If this value is not set, projects will use `revision`
 by default instead.
@@ -247,13 +247,13 @@ If not supplied the remote given by the default element is used.
 
 Attribute `revision`: Name of the Git branch the manifest wants
 to track for this project.  Names can be relative to refs/heads
-(e.g. just "master") or absolute (e.g. "refs/heads/master").
+(e.g. just "main") or absolute (e.g. "refs/heads/main").
 Tags and/or explicit SHA-1s should work in theory, but have not
 been extensively tested.  If not supplied the revision given by
 the remote element is used if applicable, else the default
 element is used.
 
-Attribute `dest-branch`: Name of a Git branch (e.g. `master`).
+Attribute `dest-branch`: Name of a Git branch (e.g. `main`).
 When using `repo upload`, changes will be submitted for code
 review on this branch. If unspecified both here and in the
 default element, `revision` is used instead.

docs/python-support.md

@@ -18,13 +18,13 @@ Bugfixes may be added on a best-effort basis or from the community, but largely
 no new features will be added, nor is support guaranteed.
 
 Users can select this during `repo init` time via the [repo launcher].
-Otherwise the default branches (e.g. stable & master) will be used which will
+Otherwise the default branches (e.g. stable & main) will be used which will
 require Python 3.
 
 This means the [repo launcher] needs to support both Python 2 & Python 3, but
 since it doesn't import any other repo code, this shouldn't be too problematic.
 
-The master branch will require Python 3.6 at a minimum.
+The main branch will require Python 3.6 at a minimum.
 If the system has an older version of Python 3, then users will have to select
 the legacy Python 2 branch instead.
 

docs/release-process.md

@@ -97,7 +97,7 @@ If that tag cannot be verified, it gives up and forces the user to resolve.
 
 ## Branch management
 
-All development happens on the `master` branch and should generally be stable.
+All development happens on the `main` branch and should generally be stable.
 
 Since the repo launcher defaults to tracking the `stable` branch, it is not
 normally updated until a new release is available.
@@ -112,7 +112,7 @@ For example, when `stable` moves from `v1.10.x` to `v1.11.x`, then the `maint`
 branch will be updated from `v1.9.x` to `v1.10.x`.
 
 We don't have parallel release branches/series.
-Typically all tags are made against the `master` branch and then pushed to the
+Typically all tags are made against the `main` branch and then pushed to the
 `stable` branch to make it available to the rest of the world.
 Since repo doesn't typically see a lot of changes, this tends to be OK.
 
@@ -120,10 +120,10 @@ Since repo doesn't typically see a lot of changes, this tends to be OK.
 
 When you want to create a new release, you'll need to select a good version and
 create a signed tag using a key registered in repo itself.
-Typically we just tag the latest version of the `master` branch.
+Typically we just tag the latest version of the `main` branch.
 The tag could be pushed now, but it won't be used by clients normally (since the
 default `repo-rev` setting is `stable`).
-This would allow some early testing on systems who explicitly select `master`.
+This would allow some early testing on systems who explicitly select `main`.
 
 ### Creating a signed tag
 
@@ -144,7 +144,7 @@ $ export GNUPGHOME=~/.gnupg/repo/
 $ gpg -K
 
 # Pick whatever branch or commit you want to tag.
-$ r=master
+$ r=main
 
 # Pick the new version.
 $ t=1.12.10

docs/repo-hooks.md

@@ -27,7 +27,7 @@ repohooks project is updated and a hook is triggered.
 For the full syntax, see the [repo manifest format](./manifest-format.md).
 
 Here's a short example from
-[Android](https://android.googlesource.com/platform/manifest/+/master/default.xml).
+[Android](https://android.googlesource.com/platform/manifest/+/HEAD/default.xml).
 The `<project>` line checks out the repohooks git repo to the local
 `tools/repohooks/` path.  The `<repo-hooks>` line says to look in the project
 with the name `platform/tools/repohooks` for hooks to run during the