Add the --choose subcommand

The `--choose` subcommand runs a chooser to select a recipe to run. The
chooser should read lines containing recipe names from standard input,
and write one of those names to standard output.

The chooser defaults to `fzf`, a popular fuzzy finder, but can be
overridden by setting $JUST_CHOOSER or passing `--chooser <CHOOSER>`.

.github/workflows/build.yaml

@@ -10,6 +10,12 @@ on:
     branches:
     - master
 
+env:
+  # Increment to invalidate github actions caches if they become corrupt.
+  # Errors of the form "can't find crate for `snafu_derive` which `snafu` depends on"
+  # can usually be fixed by incrementing this value.
+  CACHE_KEY_PREFIX: 1
+
 jobs:
   all:
     name: All
@@ -41,19 +47,19 @@ jobs:
       uses: actions/cache@v1
       with:
         path: ~/.cargo/registry
-        key: 0-${{ runner.os }}-cargo-registry-${{ hashFiles('**/Cargo.lock') }}
+        key: ${{ env.CACHE_KEY_PREFIX }}-${{ runner.os }}-cargo-registry-${{ hashFiles('**/Cargo.lock') }}
 
     - name: Cache cargo index
       uses: actions/cache@v1
       with:
         path: ~/.cargo/git
-        key: 0-${{ runner.os }}-cargo-index-${{ hashFiles('**/Cargo.lock') }}
+        key: ${{ env.CACHE_KEY_PREFIX }}-${{ runner.os }}-cargo-index-${{ hashFiles('**/Cargo.lock') }}
 
     - name: Cache cargo build
       uses: actions/cache@v1
       with:
         path: target
-        key: 0-${{ runner.os }}-cargo-build-target-${{ hashFiles('**/Cargo.lock') }}
+        key: ${{ env.CACHE_KEY_PREFIX }}-${{ runner.os }}-cargo-build-target-${{ hashFiles('**/Cargo.lock') }}
 
     - name: Install Main Toolchain
       uses: actions-rs/toolchain@v1

README.adoc

@@ -266,6 +266,14 @@ $ just --summary --unsorted
 test build
 ```
 
+If you'd like `just` to default to listing the recipes in the justfile, you can
+use this as your default recipe:
+
+```make
+default:
+  @just --list
+```
+
 === Aliases
 
 Aliases allow recipes to be invoked with alternative names:
@@ -958,6 +966,35 @@ echo 'Bar!'
 Bar!
 ```
 
+=== Selecting a Recipe to Run With an Interactive Chooser
+
+The `--choose` subcommand makes just invoke a chooser to select which recipe to
+run. Choosers should read lines containing recipe names from standard input and
+print one of those names to standard output.
+
+Because there is currenly no way to run a recipe that requires arguments with
+`--choose`, such recipes will not be given to the chooser. Private recipes and
+aliases are also skipped.
+
+The chooser can be overridden with the `--chooser` flag. If `--chooser` is not
+given, then `just` first checks if `$JUST_CHOOSER` is set. If it isn't, then
+the chooser defaults to `fzf`, a popular fuzzy finder.
+
+Arguments can be included in the chooser, i.e. `fzf --exact`.
+
+The chooser is invoked in the same way as recipe lines. For example, if the
+chooser is `fzf`, it will be invoked with `sh -cu 'fzf'`, and if the shell, or
+the shell arguments are overridden, the chooser invocation will respect those
+overrides.
+
+If you'd like `just` to default to selecting a recipe with a chooser, you can
+use this as your default recipe:
+
+```make
+default:
+  @just --choose
+```
+
 === Invoking Justfiles in Other Directories
 
 If the first argument passed to `just` contains a `/`, then the following occurs:

completions/just.bash

@@ -20,13 +20,17 @@ _just() {
 
     case "${cmd}" in
         just)
-            opts=" -q -u -v -e -l -h -V -f -d -s  --dry-run --highlight --no-dotenv --no-highlight --quiet --clear-shell-args --unsorted --verbose --dump --edit --evaluate --init --list --summary --variables --help --version --color --justfile --set --shell --shell-arg --working-directory --completions --show  <ARGUMENTS>... "
+            opts=" -q -u -v -e -l -h -V -f -d -s  --dry-run --highlight --no-dotenv --no-highlight --quiet --clear-shell-args --unsorted --verbose --choose --dump --edit --evaluate --init --list --summary --variables --help --version --chooser --color --justfile --set --shell --shell-arg --working-directory --completions --show  <ARGUMENTS>... "
             if [[ ${cur} == -* || ${COMP_CWORD} -eq 1 ]] ; then
                 COMPREPLY=( $(compgen -W "${opts}" -- "${cur}") )
                 return 0
             fi
             case "${prev}" in
 
+                --chooser)
+                    COMPREPLY=($(compgen -f "${cur}"))
+                    return 0
+                    ;;
                 --color)
                     COMPREPLY=($(compgen -W "auto always never" -- "${cur}"))
                     return 0

completions/just.elvish

@@ -14,6 +14,7 @@ edit:completion:arg-completer[just] = [@words]{
     }
     completions = [
         &'just'= {
+            cand --chooser 'Override binary invoked by `--choose`'
             cand --color 'Print colorful output'
             cand -f 'Use <JUSTFILE> as justfile.'
             cand --justfile 'Use <JUSTFILE> as justfile.'
@@ -36,6 +37,7 @@ edit:completion:arg-completer[just] = [@words]{
             cand --unsorted 'Return list and summary entries in source order'
             cand -v 'Use verbose output'
             cand --verbose 'Use verbose output'
+            cand --choose 'Select a recipe to run using a binary. If `--chooser` is not passed the chooser defaults to the value of $JUST_CHOOSER, falling back to `fzf`'
             cand --dump 'Print entire justfile'
             cand -e 'Edit justfile with editor given by $VISUAL or $EDITOR, falling back to `vim`'
             cand --edit 'Edit justfile with editor given by $VISUAL or $EDITOR, falling back to `vim`'

completions/just.fish

@@ -9,6 +9,7 @@ complete -c just -n "__fish_is_first_arg" --no-files
 complete -c just -a '(__fish_just_complete_recipes)'
 
 # autogenerated completions
+complete -c just -n "__fish_use_subcommand" -l chooser -d 'Override binary invoked by `--choose`'
 complete -c just -n "__fish_use_subcommand" -l color -d 'Print colorful output' -r -f -a "auto always never"
 complete -c just -n "__fish_use_subcommand" -s f -l justfile -d 'Use <JUSTFILE> as justfile.'
 complete -c just -n "__fish_use_subcommand" -l set -d 'Override <VARIABLE> with <VALUE>'
@@ -25,6 +26,7 @@ complete -c just -n "__fish_use_subcommand" -s q -l quiet -d 'Suppress all outpu
 complete -c just -n "__fish_use_subcommand" -l clear-shell-args -d 'Clear shell arguments'
 complete -c just -n "__fish_use_subcommand" -s u -l unsorted -d 'Return list and summary entries in source order'
 complete -c just -n "__fish_use_subcommand" -s v -l verbose -d 'Use verbose output'
+complete -c just -n "__fish_use_subcommand" -l choose -d 'Select a recipe to run using a binary. If `--chooser` is not passed the chooser defaults to the value of $JUST_CHOOSER, falling back to `fzf`'
 complete -c just -n "__fish_use_subcommand" -l dump -d 'Print entire justfile'
 complete -c just -n "__fish_use_subcommand" -s e -l edit -d 'Edit justfile with editor given by $VISUAL or $EDITOR, falling back to `vim`'
 complete -c just -n "__fish_use_subcommand" -l evaluate -d 'Print evaluated variables'

completions/just.powershell

@@ -19,6 +19,7 @@ Register-ArgumentCompleter -Native -CommandName 'just' -ScriptBlock {
 
     $completions = @(switch ($command) {
         'just' {
+            [CompletionResult]::new('--chooser', 'chooser', [CompletionResultType]::ParameterName, 'Override binary invoked by `--choose`')
             [CompletionResult]::new('--color', 'color', [CompletionResultType]::ParameterName, 'Print colorful output')
             [CompletionResult]::new('-f', 'f', [CompletionResultType]::ParameterName, 'Use <JUSTFILE> as justfile.')
             [CompletionResult]::new('--justfile', 'justfile', [CompletionResultType]::ParameterName, 'Use <JUSTFILE> as justfile.')
@@ -41,6 +42,7 @@ Register-ArgumentCompleter -Native -CommandName 'just' -ScriptBlock {
             [CompletionResult]::new('--unsorted', 'unsorted', [CompletionResultType]::ParameterName, 'Return list and summary entries in source order')
             [CompletionResult]::new('-v', 'v', [CompletionResultType]::ParameterName, 'Use verbose output')
             [CompletionResult]::new('--verbose', 'verbose', [CompletionResultType]::ParameterName, 'Use verbose output')
+            [CompletionResult]::new('--choose', 'choose', [CompletionResultType]::ParameterName, 'Select a recipe to run using a binary. If `--chooser` is not passed the chooser defaults to the value of $JUST_CHOOSER, falling back to `fzf`')
             [CompletionResult]::new('--dump', 'dump', [CompletionResultType]::ParameterName, 'Print entire justfile')
             [CompletionResult]::new('-e', 'e', [CompletionResultType]::ParameterName, 'Edit justfile with editor given by $VISUAL or $EDITOR, falling back to `vim`')
             [CompletionResult]::new('--edit', 'edit', [CompletionResultType]::ParameterName, 'Edit justfile with editor given by $VISUAL or $EDITOR, falling back to `vim`')

completions/just.zsh

@@ -15,6 +15,7 @@ _just() {
 
     local context curcontext="$curcontext" state line
     local common=(
+'--chooser=[Override binary invoked by `--choose`]' \
 '--color=[Print colorful output]: :(auto always never)' \
 '-f+[Use <JUSTFILE> as justfile.]' \
 '--justfile=[Use <JUSTFILE> as justfile.]' \
@@ -37,6 +38,7 @@ _just() {
 '--unsorted[Return list and summary entries in source order]' \
 '*-v[Use verbose output]' \
 '*--verbose[Use verbose output]' \
+'--choose[Select a recipe to run using a binary. If `--chooser` is not passed the chooser defaults to the value of $JUST_CHOOSER, falling back to `fzf`]' \
 '--dump[Print entire justfile]' \
 '-e[Edit justfile with editor given by $VISUAL or $EDITOR, falling back to `vim`]' \
 '--edit[Edit justfile with editor given by $VISUAL or $EDITOR, falling back to `vim`]' \

src/common.rs

@@ -4,13 +4,14 @@ pub(crate) use std::{
   cmp,
   collections::{BTreeMap, BTreeSet},
   env,
+  ffi::OsString,
   fmt::{self, Debug, Display, Formatter},
   fs,
   io::{self, Cursor, Write},
   iter::{self, FromIterator},
   ops::{Index, Range, RangeInclusive},
   path::{Path, PathBuf},
-  process::{self, Command},
+  process::{self, Command, Stdio},
   rc::Rc,
   str::{self, Chars},
   sync::{Mutex, MutexGuard},