contrib/bash_completion

cborutil: implement sans I/O decoder

The vendored CBOR package decodes by calling read(n) on an object.
There are a number of disadvantages to this:

* Uses blocking I/O. If sufficient data is not available, the decoder
  will hang until it is.
* No support for partial reads. If the read(n) returns less data than
  requested, the decoder raises an error.
* Requires the use of a file like object. If the original data is in
  say a buffer, we need to "cast" it to e.g. a BytesIO to appease the
  decoder.

In addition, the vendored CBOR decoder doesn't provide flexibility
that we desire. Specifically:

* It buffers indefinite length bytestrings instead of streaming them.
* It doesn't allow limiting the set of types that can be decoded. This
  property is useful when implementing a "hardened" decoder that is
  less susceptible to abusive input.
* It doesn't provide sufficient "hook points" and introspection to
  institute checks around behavior. These are useful for implementing
  a "hardened" decoder.

This all adds up to a reasonable set of justifications for writing our
own decoder.

So, this commit implements our own CBOR decoder.

At the heart of the decoder is a function that decodes a single "item"
from a buffer. This item can be a complete simple value or a special
value, such as "start of array." Using this function, we can build a
decoder that effectively iterates over the stream of decoded items and
builds up higher-level values, such as arrays, maps, sets, and indefinite
length bytestrings. And we can do this without performing I/O in the
decoder itself.

The core of the sans I/O decoder will probably not be used directly.
Instead, it is expected that we'll build utility functions for invoking
the decoder given specific input types. This will allow extreme
flexibility in how data is delivered to the decoder.

I'm pretty happy with the state of the decoder modulo the TODO items
to track wanted features to help with a "hardened" decoder. The one
thing I could be convinced to change is the handling of semantic tags.
Since we only support a single semantic tag (sets), I thought it would
be easier to handle them inline in decodeitem(). This is simpler now.
But if we add support for other semantic tags, it will likely be easier
to move semantic tag handling outside of decodeitem(). But, properly
supporting semantic tags opens up a whole can of worms, as many
semantic tags imply new types. I'm optimistic we won't need these in
Mercurial. But who knows.

I'm also pretty happy with the test coverage. Writing comprehensive
tests for partial decoding did flush out a handful of bugs. One
general improvement to testing would be fuzz testing for partial
decoding. I may implement that later. I also anticipate switching the
wire protocol code to this new decoder will flush out any lingering
bugs.

Differential Revision: https://phab.mercurial-scm.org/D4414

# bash completion for the Mercurial distributed SCM -*- sh -*-

# Docs:
#
# If you source this file from your .bashrc, bash should be able to
# complete a command line that uses hg with all the available commands
# and options and sometimes even arguments.
#
# Mercurial allows you to define additional commands through extensions.
# Bash should be able to automatically figure out the name of these new
# commands and their options.  See below for how to define _hg_opt_foo
# and _hg_cmd_foo functions to fine-tune the completion for option and
# non-option arguments, respectively.
#
#
# Notes about completion for specific commands:
#
# - the completion function for the email command from the patchbomb
#   extension will try to call _hg_emails to get a list of e-mail
#   addresses.  It's up to the user to define this function.  For
#   example, put the addresses of the lists that you usually patchbomb
#   in ~/.patchbomb-to and the addresses that you usually use to send
#   the patchbombs in ~/.patchbomb-from and use something like this:
#
#      _hg_emails()
#      {
#          if [ -r ~/.patchbomb-$1 ]; then
#              cat ~/.patchbomb-$1
#          fi
#      }
#
#
# Writing completion functions for additional commands:
#
# If it exists, the function _hg_cmd_foo will be called without
# arguments to generate the completion candidates for the hg command
# "foo".  If the command receives some arguments that aren't options
# even though they start with a "-", you can define a function called
# _hg_opt_foo to generate the completion candidates.  If _hg_opt_foo
# doesn't return 0, regular completion for options is attempted.
#
# In addition to the regular completion variables provided by bash,
# the following variables are also set:
# - $hg - the hg program being used (e.g. /usr/bin/hg)
# - $cmd - the name of the hg command being completed
# - $cmd_index - the index of $cmd in $COMP_WORDS
# - $cur - the current argument being completed
# - $prev - the argument before $cur
# - $global_args - "|"-separated list of global options that accept
#                  an argument (e.g. '--cwd|-R|--repository')
# - $canonical - 1 if we canonicalized $cmd before calling the function
#                0 otherwise
#

shopt -s extglob

_hg_cmd()
{
    HGPLAIN=1 "$hg" "$@" 2>/dev/null
}

_hg_commands()
{
    local commands
    commands="$(HGPLAINEXCEPT=alias _hg_cmd debugcomplete "$cur")" || commands=""
    COMPREPLY=(${COMPREPLY[@]:-} $(compgen -W '$commands' -- "$cur"))
}

_hg_paths()
{
    local paths="$(_hg_cmd paths -q)"
    COMPREPLY=(${COMPREPLY[@]:-} $(compgen -W '$paths' -- "$cur"))
}

_hg_repos()
{
    local i
    for i in $(compgen -d -- "$cur"); do
        test ! -d "$i"/.hg || COMPREPLY=(${COMPREPLY[@]:-} "$i")
    done
}

_hg_debugpathcomplete()
{
    local files="$(_hg_cmd debugpathcomplete $1 "$cur")"
    local IFS=$'\n'
    COMPREPLY=(${COMPREPLY[@]:-} $(compgen -W '$files' -- "$cur"))
}

_hg_status()
{
    if [ -z "$HGCOMPLETE_NOSTATUS" ]; then
        local files="$(_hg_cmd status -n$1 "glob:$cur**")"
        local IFS=$'\n'
        COMPREPLY=(${COMPREPLY[@]:-} $(compgen -W '$files' -- "$cur"))
    fi
}

_hg_branches()
{
    local branches="$(_hg_cmd branches -q)"
    local IFS=$'\n'
    COMPREPLY=(${COMPREPLY[@]:-} $(compgen -W '$branches' -- "$cur"))
}

_hg_bookmarks()
{
    local bookmarks="$(_hg_cmd bookmarks -q)"
    local IFS=$'\n'
    COMPREPLY=(${COMPREPLY[@]:-} $(compgen -W '$bookmarks' -- "$cur"))
}

_hg_labels()
{
    local labels="$(_hg_cmd debugnamecomplete "$cur")"
    local IFS=$'\n'
    COMPREPLY=(${COMPREPLY[@]:-} $(compgen -W '$labels' -- "$cur"))
}

# this is "kind of" ugly...
_hg_count_non_option()
{
    local i count=0
    local filters="$1"

    for ((i=1; $i<=$COMP_CWORD; i++)); do
        if [[ "${COMP_WORDS[i]}" != -* ]]; then
            if [[ ${COMP_WORDS[i-1]} == @($filters|$global_args) ]]; then
                continue
            fi
            count=$(($count + 1))
        fi
    done

    echo $(($count - 1))
}

_hg_fix_wordlist()
{
    local LASTCHAR=' '
    if [ ${#COMPREPLY[@]} = 1 ]; then
        [ -d "$COMPREPLY" ] && LASTCHAR=/
        COMPREPLY=$(printf %q%s "$COMPREPLY" "$LASTCHAR")
    else
        for ((i=0; i < ${#COMPREPLY[@]}; i++)); do
            [ -d "${COMPREPLY[$i]}" ] && COMPREPLY[$i]=${COMPREPLY[$i]}/
        done
    fi
}

_hg()
{
    local cur prev cmd cmd_index opts i aliashg
    # global options that receive an argument
    local global_args='--cwd|-R|--repository|--color|--config|--encoding|--encodingmode|--pager'
    local hg="$1"
    local canonical=0

    aliashg=$(alias $hg 2>/dev/null)
    if [[ -n "$aliashg" ]]; then
      aliashg=${aliashg#"alias $hg='"}
      aliashg=${aliashg%"'"}
      hg=$aliashg
    fi

    COMPREPLY=()
    cur="$2"
    prev="$3"

    # searching for the command
    # (first non-option argument that doesn't follow a global option that
    #  receives an argument)
    for ((i=1; $i<=$COMP_CWORD; i++)); do
        if [[ ${COMP_WORDS[i]} != -* ]]; then
            if [[ ${COMP_WORDS[i-1]} != @($global_args) ]]; then
                cmd="${COMP_WORDS[i]}"
                cmd_index=$i
                break
            fi
        fi
    done

    if [[ "$cur" == -* ]]; then
        if [ "$(type -t "_hg_opt_$cmd")" = function ] && "_hg_opt_$cmd"; then
            _hg_fix_wordlist
            return
        fi

        opts=$(HGPLAINEXCEPT=alias _hg_cmd debugcomplete --options "$cmd")

        COMPREPLY=(${COMPREPLY[@]:-} $(compgen -W '$opts' -- "$cur"))
        _hg_fix_wordlist
        return
    fi

    # global options
    case "$prev" in
        -R|--repository)
            _hg_paths
            _hg_repos
            _hg_fix_wordlist
            return
        ;;
        --cwd)
            # Stick with default bash completion
            _hg_fix_wordlist
            return
        ;;
        --color)
            local choices='true false yes no always auto never debug'
            COMPREPLY=(${COMPREPLY[@]:-} $(compgen -W '$choices' -- "$cur"))
            _hg_fix_wordlist
            return
        ;;
        --pager)
            local choices='true false yes no always auto never'
            COMPREPLY=(${COMPREPLY[@]:-} $(compgen -W '$choices' -- "$cur"))
            _hg_fix_wordlist
            return
        ;;
    esac

    if [ -z "$cmd" ] || [ $COMP_CWORD -eq $i ]; then
        _hg_commands
        _hg_fix_wordlist
        return
    fi

    # try to generate completion candidates for whatever command the user typed
    local help
    if _hg_command_specific; then
        _hg_fix_wordlist
        return
    fi

    # canonicalize the command name and try again
    help=$(_hg_cmd help "$cmd")
    if [ $? -ne 0 ]; then
        # Probably either the command doesn't exist or it's ambiguous
        return
    fi
    cmd=${help#hg }
    cmd=${cmd%%[$' \n']*}
    canonical=1
    _hg_command_specific
    _hg_fix_wordlist
}

_hg_command_specific()
{
    if [ "$(type -t "_hg_cmd_$cmd")" = function ]; then
        "_hg_cmd_$cmd"
        return 0
    fi

    if [ "$cmd" != status ]; then
        case "$prev" in
            -r|--rev)
                if [[ $canonical = 1 || status != "$cmd"* ]]; then
                    _hg_labels
                    return 0
                fi
                return 1
            ;;
            -B|--bookmark)
                if [[ $canonical = 1 || status != "$cmd"* ]]; then
                    _hg_bookmarks
                    return 0
                fi
                return 1
            ;;
            -b|--branch)
                if [[ $canonical = 1 || status != "$cmd"* ]]; then
                    _hg_branches
                    return 0
                fi
                return 1
            ;;
        esac
    fi

    local aliascmd=$(_hg_cmd showconfig alias.$cmd | awk '{print $1}')
    [ -n "$aliascmd" ] && cmd=$aliascmd

    case "$cmd" in
        help)
            _hg_commands
        ;;
        export)
            if _hg_ext_mq_patchlist qapplied && [ "${COMPREPLY[*]}" ]; then
                return 0
            fi
            _hg_labels
        ;;
        manifest|update|up|checkout|co)
            _hg_labels
        ;;
        pull|push|outgoing|incoming)
            _hg_paths
            _hg_repos
        ;;
        paths)
            _hg_paths
        ;;
        add)
            _hg_status "u"
        ;;
        merge)
            _hg_labels
        ;;
        commit|ci|record|amend)
            _hg_status "mar"
        ;;
        remove|rm)
            _hg_debugpathcomplete -n
        ;;
        forget)
            _hg_debugpathcomplete -fa
        ;;
        diff)
            _hg_status "mar"
        ;;
        revert)
            _hg_status "mard"
        ;;
        clone)
            local count=$(_hg_count_non_option)
            if [ $count = 1 ]; then
                _hg_paths
            fi
            _hg_repos
        ;;
        debugindex|debugindexdot)
            COMPREPLY=(${COMPREPLY[@]:-} $(compgen -f -X "!*.i" -- "$cur"))
        ;;
        debugdata)
            COMPREPLY=(${COMPREPLY[@]:-} $(compgen -f -X "!*.d" -- "$cur"))
        ;;
        *)
            return 1
        ;;
    esac

    return 0
}

complete -o bashdefault -o default -o nospace -F _hg hg \
    || complete -o default -o nospace -F _hg hg


# Completion for commands provided by extensions

# bookmarks
_hg_cmd_bookmarks()
{
    _hg_bookmarks
    return
}

# mq
_hg_ext_mq_patchlist()
{
    local patches
    patches=$(_hg_cmd $1)
    if [ $? -eq 0 ] && [ "$patches" ]; then
        COMPREPLY=(${COMPREPLY[@]:-} $(compgen -W '$patches' -- "$cur"))
        return 0
    fi
    return 1
}

_hg_ext_mq_queues()
{
    local root=$(_hg_cmd root)
    local n
    for n in $(cd "$root"/.hg && compgen -d -- "$cur"); do
        # I think we're usually not interested in the regular "patches" queue
        # so just filter it.
        if [ "$n" != patches ] && [ -e "$root/.hg/$n/series" ]; then
            COMPREPLY=(${COMPREPLY[@]:-} "$n")
        fi
    done
}

_hg_cmd_qpop()
{
    if [[ "$prev" = @(-n|--name) ]]; then
        _hg_ext_mq_queues
        return
    fi
    _hg_ext_mq_patchlist qapplied
}

_hg_cmd_qpush()
{
    if [[ "$prev" = @(-n|--name) ]]; then
        _hg_ext_mq_queues
        return
    fi
    _hg_ext_mq_patchlist qunapplied
}

_hg_cmd_qgoto()
{
    if [[ "$prev" = @(-n|--name) ]]; then
        _hg_ext_mq_queues
        return
    fi
    _hg_ext_mq_patchlist qseries
}

_hg_cmd_qdelete()
{
    local qcmd=qunapplied
    if [[ "$prev" = @(-r|--rev) ]]; then
        qcmd=qapplied
    fi
    _hg_ext_mq_patchlist $qcmd
}

_hg_cmd_qfinish()
{
    if [[ "$prev" = @(-a|--applied) ]]; then
        return
    fi
    _hg_ext_mq_patchlist qapplied
}

_hg_cmd_qsave()
{
    if [[ "$prev" = @(-n|--name) ]]; then
        _hg_ext_mq_queues
        return
    fi
}

_hg_cmd_rebase() {
   if [[ "$prev" = @(-s|--source|-d|--dest|-b|--base|-r|--rev) ]]; then
       _hg_labels
       return
   fi
}

_hg_cmd_strip()
{
    if [[ "$prev" = @(-B|--bookmark) ]]; then
        _hg_bookmarks
        return
    fi
    _hg_labels
}

_hg_cmd_qcommit()
{
    local root=$(_hg_cmd root)
    # this is run in a sub-shell, so we can't use _hg_status
    local files=$(cd "$root/.hg/patches" && _hg_cmd status -nmar)
    COMPREPLY=(${COMPREPLY[@]:-} $(compgen -W '$files' -- "$cur"))
}

_hg_cmd_qfold()
{
    _hg_ext_mq_patchlist qunapplied
}

_hg_cmd_qrename()
{
    _hg_ext_mq_patchlist qseries
}

_hg_cmd_qheader()
{
    _hg_ext_mq_patchlist qseries
}

_hg_cmd_qclone()
{
    local count=$(_hg_count_non_option)
    if [ $count = 1 ]; then
        _hg_paths
    fi
    _hg_repos
}

_hg_ext_mq_guards()
{
    _hg_cmd qselect --series | sed -e 's/^.//'
}

_hg_cmd_qselect()
{
    local guards=$(_hg_ext_mq_guards)
    COMPREPLY=(${COMPREPLY[@]:-} $(compgen -W '$guards' -- "$cur"))
}

_hg_cmd_qguard()
{
    local prefix=''

    if [[ "$cur" == +* ]]; then
        prefix=+
    elif [[ "$cur" == -* ]]; then
        prefix=-
    fi
    local ncur=${cur#[-+]}

    if ! [ "$prefix" ]; then
        _hg_ext_mq_patchlist qseries
        return
    fi

    local guards=$(_hg_ext_mq_guards)
    COMPREPLY=(${COMPREPLY[@]:-} $(compgen -P $prefix -W '$guards' -- "$ncur"))
}

_hg_opt_qguard()
{
    local i
    for ((i=cmd_index+1; i<=COMP_CWORD; i++)); do
        if [[ ${COMP_WORDS[i]} != -* ]]; then
            if [[ ${COMP_WORDS[i-1]} != @($global_args) ]]; then
                _hg_cmd_qguard
                return 0
            fi
        elif [ "${COMP_WORDS[i]}" = -- ]; then
            _hg_cmd_qguard
            return 0
        fi
    done
    return 1
}

_hg_cmd_qqueue()
{
    local q
    local queues
    local opts="--list --create --rename --delete --purge"

    queues=$( _hg_cmd qqueue --quiet )

    COMPREPLY=( $( compgen -W "${opts} ${queues}" "${cur}" ) )
}


# hbisect
_hg_cmd_bisect()
{
    local i subcmd

    # find the sub-command
    for ((i=cmd_index+1; i<=COMP_CWORD; i++)); do
        if [[ ${COMP_WORDS[i]} != -* ]]; then
            if [[ ${COMP_WORDS[i-1]} != @($global_args) ]]; then
                subcmd="${COMP_WORDS[i]}"
                break
            fi
        fi
    done

    if [ -z "$subcmd" ] || [ $COMP_CWORD -eq $i ] || [ "$subcmd" = help ]; then
        COMPREPLY=(${COMPREPLY[@]:-}
                   $(compgen -W 'bad good help init next reset' -- "$cur"))
        return
    fi

    case "$subcmd" in
        good|bad)
            _hg_labels
            ;;
    esac

    return
}


# patchbomb
_hg_cmd_email()
{
    case "$prev" in
        -c|--cc|-t|--to|-f|--from|--bcc)
            # we need an e-mail address. let the user provide a function
            # to get them
            if [ "$(type -t _hg_emails)" = function ]; then
                local arg=to
                if [[ "$prev" == @(-f|--from) ]]; then
                    arg=from
                fi
                local addresses=$(_hg_emails $arg)
                COMPREPLY=(${COMPREPLY[@]:-}
                           $(compgen -W '$addresses' -- "$cur"))
            fi
            return
            ;;
        -m|--mbox)
            # fallback to standard filename completion
            return
            ;;
        -s|--subject)
            # free form string
            return
            ;;
    esac

    _hg_labels
    return
}


# gpg
_hg_cmd_sign()
{
    _hg_labels
}


# transplant
_hg_cmd_transplant()
{
    case "$prev" in
        -s|--source)
            _hg_paths
            _hg_repos
            return
            ;;
        --filter)
            # standard filename completion
            return
            ;;
    esac

    # all other transplant options values and command parameters are revisions
    _hg_labels
    return
}

# shelve
_hg_shelves()
{
    local shelves="$(_hg_cmd shelve -ql)"
    local IFS=$'\n'
    COMPREPLY=(${COMPREPLY[@]:-} $(compgen -W '$shelves' -- "$cur"))
}

_hg_cmd_shelve()
{
    if [[ "$prev" = @(-d|--delete|-l|--list|-p|--patch|--stat) ]]; then
        _hg_shelves
    else
        _hg_status "mard"
    fi
}

_hg_cmd_unshelve()
{
    _hg_shelves
}