client: rename "master" branch references to "main"

Signed-off-by: Gyuho Lee <leegyuho@amazon.com>

client/v3/README.md

@@ -77,7 +77,7 @@ if err != nil {
 
 ## Metrics
 
-The etcd client optionally exposes RPC metrics through [go-grpc-prometheus](https://github.com/grpc-ecosystem/go-grpc-prometheus). See the [examples](https://github.com/etcd-io/etcd/blob/master/tests/integration/clientv3/examples/example_metrics_test.go).
+The etcd client optionally exposes RPC metrics through [go-grpc-prometheus](https://github.com/grpc-ecosystem/go-grpc-prometheus). See the [examples](https://github.com/etcd-io/etcd/blob/main/tests/integration/clientv3/examples/example_metrics_test.go).
 
 ## Namespacing
 
@@ -89,4 +89,4 @@ Client request size limit is configurable via `clientv3.Config.MaxCallSendMsgSiz
 
 ## Examples
 
-More code [examples](https://github.com/etcd-io/etcd/tree/master/tests/integration/clientv3/examples) can be found at [GoDoc](https://pkg.go.dev/go.etcd.io/etcd/client/v3).
+More code [examples](https://github.com/etcd-io/etcd/tree/main/tests/integration/clientv3/examples) can be found at [GoDoc](https://pkg.go.dev/go.etcd.io/etcd/client/v3).

client/v3/doc.go

@@ -61,7 +61,7 @@
 //
 //  1. context error: canceled or deadline exceeded.
 //  2. gRPC error: e.g. when clock drifts in server-side before client's context deadline exceeded.
-//  See https://github.com/etcd-io/etcd/blob/master/api/v3rpc/rpctypes/error.go
+//  See https://github.com/etcd-io/etcd/blob/main/api/v3rpc/rpctypes/error.go
 //
 // Here is the example code to handle client errors:
 //

etcdctl/README.md

@@ -3,7 +3,7 @@ etcdctl
 
 `etcdctl` is a command line client for [etcd][etcd].
 
-The v3 API is used by default on master branch. For the v2 API, make sure to set environment variable `ETCDCTL_API=2`. See also [READMEv2][READMEv2].
+The v3 API is used by default on main branch. For the v2 API, make sure to set environment variable `ETCDCTL_API=2`. See also [READMEv2][READMEv2].
 
 If using released versions earlier than v3.4, set `ETCDCTL_API=3` to use v3 API.
 

etcdctl/READMEv2.md

@@ -328,7 +328,7 @@ Releases will follow lockstep with the etcd release cycle.
 
 etcdctl is under the Apache 2.0 license. See the [LICENSE][license] file for details.
 
-[authentication]: https://github.com/etcd-io/website/blob/master/content/docs/v2/authentication.md
+[authentication]: https://github.com/etcd-io/website/blob/main/content/docs/v2/authentication.md
 [etcd]: https://github.com/coreos/etcd
 [github-release]: https://github.com/coreos/etcd/releases/
 [license]: ../LICENSE

etcdctl/ctlv2/command/member_commands.go

@@ -164,7 +164,7 @@ func actionMemberRemove(c *cli.Context) error {
 		if m.Name == removalID {
 			// Note that, so long as it's not ambiguous, we *could* do the right thing by name here.
 			fmt.Fprintf(os.Stderr, "Found a member named %s; if this is correct, please use its ID, eg:\n\tetcdctl member remove %s\n", m.Name, m.ID)
-			fmt.Fprintf(os.Stderr, "For more details, read the documentation at https://github.com/etcd-io/etcd/blob/master/Documentation/runtime-configuration.md#remove-a-member\n\n")
+			fmt.Fprintf(os.Stderr, "For more details, read the documentation at https://github.com/etcd-io/etcd/blob/main/Documentation/runtime-configuration.md#remove-a-member\n\n")
 		}
 	}
 	if !foundID {