tools: bpftool: Slightly ease bash completion updates

Bash completion for bpftool gets two minor improvements in this patch.

Move the detection of attach types for "bpftool cgroup attach" outside
of the "case/esac" bloc, where we cannot reuse our variable holding the
list of supported attach types as a pattern list. After the change, we
have only one list of cgroup attach types to update when new types are
added, instead of the former two lists.

Also rename the variables holding lists of names for program types, map
types, and attach types, to make them more unique. This can make it
slightly easier to point people to the relevant variables to update, but
the main objective here is to help run a script to check that bash
completion is up-to-date with bpftool's source code.
Signed-off-by: Quentin Monnet <quentin@isovalent.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20210730215435.7095-2-quentin@isovalent.com

tools/bpf/bpftool/bash-completion/bpftool

@@ -404,8 +404,9 @@ _bpftool()
                             return 0
                             ;;
                         5)
-                            COMPREPLY=( $( compgen -W 'msg_verdict stream_verdict \
-                                stream_parser flow_dissector' -- "$cur" ) )
+                            local BPFTOOL_PROG_ATTACH_TYPES='msg_verdict \
+                                stream_verdict stream_parser flow_dissector'
+                            COMPREPLY=( $( compgen -W "$BPFTOOL_PROG_ATTACH_TYPES" -- "$cur" ) )
                             return 0
                             ;;
                         6)
@@ -464,7 +465,7 @@ _bpftool()
 
                     case $prev in
                         type)
-                            COMPREPLY=( $( compgen -W "socket kprobe \
+                            local BPFTOOL_PROG_LOAD_TYPES='socket kprobe \
                                 kretprobe classifier flow_dissector \
                                 action tracepoint raw_tracepoint \
                                 xdp perf_event cgroup/skb cgroup/sock \
@@ -479,8 +480,8 @@ _bpftool()
                                 cgroup/post_bind4 cgroup/post_bind6 \
                                 cgroup/sysctl cgroup/getsockopt \
                                 cgroup/setsockopt cgroup/sock_release struct_ops \
-                                fentry fexit freplace sk_lookup" -- \
-                                                   "$cur" ) )
+                                fentry fexit freplace sk_lookup'
+                            COMPREPLY=( $( compgen -W "$BPFTOOL_PROG_LOAD_TYPES" -- "$cur" ) )
                             return 0
                             ;;
                         id)
@@ -698,15 +699,15 @@ _bpftool()
                             return 0
                             ;;
                         type)
-                            COMPREPLY=( $( compgen -W 'hash array prog_array \
-                                perf_event_array percpu_hash percpu_array \
-                                stack_trace cgroup_array lru_hash \
+                            local BPFTOOL_MAP_CREATE_TYPES='hash array \
+                                prog_array perf_event_array percpu_hash \
+                                percpu_array stack_trace cgroup_array lru_hash \
                                 lru_percpu_hash lpm_trie array_of_maps \
                                 hash_of_maps devmap devmap_hash sockmap cpumap \
                                 xskmap sockhash cgroup_storage reuseport_sockarray \
                                 percpu_cgroup_storage queue stack sk_storage \
-                                struct_ops inode_storage task_storage' -- \
-                                                   "$cur" ) )
+                                struct_ops inode_storage task_storage'
+                            COMPREPLY=( $( compgen -W "$BPFTOOL_MAP_CREATE_TYPES" -- "$cur" ) )
                             return 0
                             ;;
                         key|value|flags|entries)
@@ -1017,34 +1018,37 @@ _bpftool()
                     return 0
                     ;;
                 attach|detach)
-                    local ATTACH_TYPES='ingress egress sock_create sock_ops \
-                        device bind4 bind6 post_bind4 post_bind6 connect4 connect6 \
+                    local BPFTOOL_CGROUP_ATTACH_TYPES='ingress egress \
+                        sock_create sock_ops device \
+                        bind4 bind6 post_bind4 post_bind6 connect4 connect6 \
                         getpeername4 getpeername6 getsockname4 getsockname6 \
                         sendmsg4 sendmsg6 recvmsg4 recvmsg6 sysctl getsockopt \
                         setsockopt sock_release'
                     local ATTACH_FLAGS='multi override'
                     local PROG_TYPE='id pinned tag name'
-                    case $prev in
-                        $command)
-                            _filedir
-                            return 0
-                            ;;
-                        ingress|egress|sock_create|sock_ops|device|bind4|bind6|\
-                        post_bind4|post_bind6|connect4|connect6|getpeername4|\
-                        getpeername6|getsockname4|getsockname6|sendmsg4|sendmsg6|\
-                        recvmsg4|recvmsg6|sysctl|getsockopt|setsockopt|sock_release)
+                    # Check for $prev = $command first
+                    if [ $prev = $command ]; then
+                        _filedir
+                        return 0
+                    # Then check for attach type. This is done outside of the
+                    # "case $prev in" to avoid writing the whole list of attach
+                    # types again as pattern to match (where we cannot reuse
+                    # our variable).
+                    elif [[ $BPFTOOL_CGROUP_ATTACH_TYPES =~ $prev ]]; then
                             COMPREPLY=( $( compgen -W "$PROG_TYPE" -- \
                                 "$cur" ) )
                             return 0
-                            ;;
+                    fi
+                    # case/esac for the other cases
+                    case $prev in
                         id)
                             _bpftool_get_prog_ids
                             return 0
                             ;;
                         *)
-                            if ! _bpftool_search_list "$ATTACH_TYPES"; then
-                                COMPREPLY=( $( compgen -W "$ATTACH_TYPES" -- \
-                                    "$cur" ) )
+                            if ! _bpftool_search_list "$BPFTOOL_CGROUP_ATTACH_TYPES"; then
+                                COMPREPLY=( $( compgen -W \
+                                    "$BPFTOOL_CGROUP_ATTACH_TYPES" -- "$cur" ) )
                             elif [[ "$command" == "attach" ]]; then
                                 # We have an attach type on the command line,
                                 # but it is not the previous word, or