bash-completion: initial import based on CrOS version

We've had a limited version of this in CrOS for a long time.  There's
nothing CrOS specific about it, so lets move it to the repo project so
everyone can utilize it.

Change-Id: I04cd94610c1100f3afcd2baf8c8e7ab13e589490
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/299202
Reviewed-by: Michael Mortensen <mmortensen@google.com>
Tested-by: Mike Frysinger <vapier@google.com>

completion.bash

@@ -0,0 +1,121 @@
+# Copyright 2021 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Programmable bash completion.  https://github.com/scop/bash-completion
+
+# Complete the list of repo subcommands.
+__complete_repo_list_commands() {
+  local repo=${COMP_WORDS[0]}
+  (
+  # Handle completions if running outside of a checkout.
+  if ! "${repo}" help --all 2>/dev/null; then
+    repo help 2>/dev/null
+  fi
+  ) | sed -n '/^  /{s/  \([^ ]\+\) .\+/\1/;p}'
+}
+
+# Complete list of all branches available in all projects in the repo client
+# checkout.
+__complete_repo_list_branches() {
+  local repo=${COMP_WORDS[0]}
+  "${repo}" branches 2>/dev/null | \
+    sed -n '/|/{s/[ *][Pp ] *\([^ ]\+\) .*/\1/;p}'
+}
+
+# Complete list of all projects available in the repo client checkout.
+__complete_repo_list_projects() {
+  local repo=${COMP_WORDS[0]}
+  "${repo}" list -n 2>/dev/null
+}
+
+# Complete the repo <command> argument.
+__complete_repo_command() {
+  if [[ ${COMP_CWORD} -ne 1 ]]; then
+    return 1
+  fi
+
+  local command=${COMP_WORDS[1]}
+  COMPREPLY=($(compgen -W "$(__complete_repo_list_commands)" -- "${command}"))
+  return 0
+}
+
+# Complete repo subcommands that take <branch> <projects>.
+__complete_repo_command_branch_projects() {
+  local current=$1
+  if [[ ${COMP_CWORD} -eq 2 ]]; then
+    COMPREPLY=($(compgen -W "$(__complete_repo_list_branches)" -- "${current}"))
+  else
+    COMPREPLY=($(compgen -W "$(__complete_repo_list_projects)" -- "${current}"))
+  fi
+}
+
+# Complete repo subcommands that take only <projects>.
+__complete_repo_command_projects() {
+  local current=$1
+  COMPREPLY=($(compgen -W "$(__complete_repo_list_projects)" -- "${current}"))
+}
+
+# Complete the repo subcommand arguments.
+__complete_repo_arg() {
+  if [[ ${COMP_CWORD} -le 1 ]]; then
+    return 1
+  fi
+
+  local command=${COMP_WORDS[1]}
+  local current=${COMP_WORDS[COMP_CWORD]}
+  case ${command} in
+  abandon|checkout)
+    __complete_repo_command_branch_projects "${current}"
+    return 0
+    ;;
+
+  branch|branches|diff|info|list|overview|prune|rebase|smartsync|stage|status|\
+  sync|upload)
+    __complete_repo_command_projects "${current}"
+    return 0
+    ;;
+
+  help)
+    if [[ ${COMP_CWORD} -eq 2 ]]; then
+      COMPREPLY=(
+        $(compgen -W "$(__complete_repo_list_commands)" -- "${current}")
+      )
+    fi
+    return 0
+    ;;
+
+  start)
+    if [[ ${COMP_CWORD} -gt 2 ]]; then
+      COMPREPLY=(
+        $(compgen -W "$(__complete_repo_list_projects)" -- "${current}")
+      )
+    fi
+    return 0
+    ;;
+
+  *)
+    return 1
+    ;;
+  esac
+}
+
+# Complete the repo arguments.
+__complete_repo() {
+  COMPREPLY=()
+  __complete_repo_command && return 0
+  __complete_repo_arg && return 0
+  return 0
+}
+
+complete -F __complete_repo repo