Repository: casey/just
Pull request #608 (2020-03-14 05:00:40)

Add `--variables` subcommand that prints variable names
Add a subcommand that prints out a space-separated list of the names of
top-level variables in the justfile.

The syntax is:

    $ just --variables
    a b c

This can be used for any purpose, but is mostly intended for completion
scripts, so that they can get the names of variables without using
`--evaluate`.

Useful for #606.


Patch:
diff --git a/.github/workflows/main.yaml b/.github/workflows/main.yaml
index 262c0b4f..4f80a080 100644
--- a/.github/workflows/main.yaml
+++ b/.github/workflows/main.yaml
@@ -61,10 +61,7 @@ jobs:
     - name: Completion Scripts
       if: matrix.os != 'windows-latest'
       run: |
-        for script in completions/*; do
-          shell=${script##*.}
-          cargo run -- --completions $shell > $script
-        done
+        ./bin/generate-completions
         git diff --no-ext-diff --quiet --exit-code
     - name: Package
       id: package
diff --git a/Cargo.lock b/Cargo.lock
index fa7a4451..b050bbee 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2,10 +2,10 @@
 # It is not intended for manual editing.
 [[package]]
 name = "aho-corasick"
-version = "0.7.8"
+version = "0.7.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "memchr 2.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "memchr 2.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -29,29 +29,29 @@ name = "atty"
 version = "0.2.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "hermit-abi 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.66 (registry+https://github.com/rust-lang/crates.io-index)",
+ "hermit-abi 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "backtrace"
-version = "0.3.43"
+version = "0.3.45"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "backtrace-sys 0.1.32 (registry+https://github.com/rust-lang/crates.io-index)",
+ "backtrace-sys 0.1.34 (registry+https://github.com/rust-lang/crates.io-index)",
  "cfg-if 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.66 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-demangle 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "backtrace-sys"
-version = "0.1.32"
+version = "0.1.34"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "cc 1.0.50 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.66 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -59,14 +59,6 @@ name = "bitflags"
 version = "1.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
-[[package]]
-name = "c2-chacha"
-version = "0.2.3"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-dependencies = [
- "ppv-lite86 0.2.6 (registry+https://github.com/rust-lang/crates.io-index)",
-]
-
 [[package]]
 name = "cc"
 version = "1.0.50"
@@ -93,25 +85,25 @@ dependencies = [
 
 [[package]]
 name = "ctor"
-version = "0.1.12"
+version = "0.1.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 1.0.14 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 1.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.16 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "ctrlc"
-version = "3.1.3"
+version = "3.1.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "nix 0.14.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "nix 0.17.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "winapi 0.3.8 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "derivative"
-version = "1.0.3"
+version = "1.0.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "proc-macro2 0.4.30 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -126,7 +118,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "doc-comment"
-version = "0.3.1"
+version = "0.3.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -147,7 +139,7 @@ dependencies = [
  "atty 0.2.14 (registry+https://github.com/rust-lang/crates.io-index)",
  "humantime 1.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "regex 1.3.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "regex 1.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "termcolor 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -158,10 +150,10 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "failure"
-version = "0.1.6"
+version = "0.1.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "backtrace 0.3.43 (registry+https://github.com/rust-lang/crates.io-index)",
+ "backtrace 0.3.45 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -170,16 +162,16 @@ version = "0.1.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "cfg-if 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.66 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
  "wasi 0.9.0+wasi-snapshot-preview1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "hermit-abi"
-version = "0.1.6"
+version = "0.1.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "libc 0.2.66 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -197,14 +189,14 @@ dependencies = [
  "ansi_term 0.12.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "atty 0.2.14 (registry+https://github.com/rust-lang/crates.io-index)",
  "clap 2.33.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "ctrlc 3.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
- "derivative 1.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "ctrlc 3.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
+ "derivative 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "dotenv 0.15.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "edit-distance 2.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "env_logger 0.7.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "executable-path 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "lazy_static 1.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.66 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "pretty_assertions 0.6.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "snafu 0.6.2 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -212,7 +204,7 @@ dependencies = [
  "tempfile 3.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "test-utilities 0.0.0",
  "unicode-width 0.1.7 (registry+https://github.com/rust-lang/crates.io-index)",
- "which 3.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "which 3.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -222,7 +214,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "libc"
-version = "0.2.66"
+version = "0.2.67"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -235,18 +227,18 @@ dependencies = [
 
 [[package]]
 name = "memchr"
-version = "2.3.0"
+version = "2.3.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "nix"
-version = "0.14.1"
+version = "0.17.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "bitflags 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "cc 1.0.50 (registry+https://github.com/rust-lang/crates.io-index)",
  "cfg-if 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.66 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
  "void 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -269,7 +261,7 @@ version = "0.6.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "ansi_term 0.11.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "ctor 0.1.12 (registry+https://github.com/rust-lang/crates.io-index)",
+ "ctor 0.1.13 (registry+https://github.com/rust-lang/crates.io-index)",
  "difference 2.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "output_vt100 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -284,7 +276,7 @@ dependencies = [
 
 [[package]]
 name = "proc-macro2"
-version = "1.0.8"
+version = "1.0.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "unicode-xid 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -305,10 +297,10 @@ dependencies = [
 
 [[package]]
 name = "quote"
-version = "1.0.2"
+version = "1.0.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "proc-macro2 1.0.8 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro2 1.0.9 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -317,18 +309,18 @@ version = "0.7.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "getrandom 0.1.14 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.66 (registry+https://github.com/rust-lang/crates.io-index)",
- "rand_chacha 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand_chacha 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand_core 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand_hc 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "rand_chacha"
-version = "0.2.1"
+version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "c2-chacha 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "ppv-lite86 0.2.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand_core 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -355,18 +347,18 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "regex"
-version = "1.3.4"
+version = "1.3.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "aho-corasick 0.7.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "memchr 2.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "regex-syntax 0.6.14 (registry+https://github.com/rust-lang/crates.io-index)",
+ "aho-corasick 0.7.10 (registry+https://github.com/rust-lang/crates.io-index)",
+ "memchr 2.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "regex-syntax 0.6.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "thread_local 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "regex-syntax"
-version = "0.6.14"
+version = "0.6.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -387,7 +379,7 @@ name = "snafu"
 version = "0.6.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "doc-comment 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "doc-comment 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "snafu-derive 0.6.2 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -396,9 +388,9 @@ name = "snafu-derive"
 version = "0.6.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "proc-macro2 1.0.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
- "syn 1.0.14 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro2 1.0.9 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 1.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "syn 1.0.16 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -418,11 +410,11 @@ dependencies = [
 
 [[package]]
 name = "syn"
-version = "1.0.14"
+version = "1.0.16"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "proc-macro2 1.0.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "proc-macro2 1.0.9 (registry+https://github.com/rust-lang/crates.io-index)",
+ "quote 1.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "unicode-xid 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -437,7 +429,7 @@ version = "3.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "cfg-if 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.66 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.7.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "redox_syscall 0.1.56 (registry+https://github.com/rust-lang/crates.io-index)",
  "remove_dir_all 0.5.2 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -507,11 +499,11 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "which"
-version = "3.1.0"
+version = "3.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "failure 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)",
- "libc 0.2.66 (registry+https://github.com/rust-lang/crates.io-index)",
+ "failure 0.1.7 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.67 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -542,57 +534,56 @@ version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [metadata]
-"checksum aho-corasick 0.7.8 (registry+https://github.com/rust-lang/crates.io-index)" = "743ad5a418686aad3b87fd14c43badd828cf26e214a00f92a384291cf22e1811"
+"checksum aho-corasick 0.7.10 (registry+https://github.com/rust-lang/crates.io-index)" = "8716408b8bc624ed7f65d223ddb9ac2d044c0547b6fa4b0d554f3a9540496ada"
 "checksum ansi_term 0.11.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ee49baf6cb617b853aa8d93bf420db2383fab46d314482ca2803b40d5fde979b"
 "checksum ansi_term 0.12.1 (registry+https://github.com/rust-lang/crates.io-index)" = "d52a9bb7ec0cf484c551830a7ce27bd20d67eac647e1befb56b0be4ee39a55d2"
 "checksum atty 0.2.14 (registry+https://github.com/rust-lang/crates.io-index)" = "d9b39be18770d11421cdb1b9947a45dd3f37e93092cbf377614828a319d5fee8"
-"checksum backtrace 0.3.43 (registry+https://github.com/rust-lang/crates.io-index)" = "7f80256bc78f67e7df7e36d77366f636ed976895d91fe2ab9efa3973e8fe8c4f"
-"checksum backtrace-sys 0.1.32 (registry+https://github.com/rust-lang/crates.io-index)" = "5d6575f128516de27e3ce99689419835fce9643a9b215a14d2b5b685be018491"
+"checksum backtrace 0.3.45 (registry+https://github.com/rust-lang/crates.io-index)" = "ad235dabf00f36301792cfe82499880ba54c6486be094d1047b02bacb67c14e8"
+"checksum backtrace-sys 0.1.34 (registry+https://github.com/rust-lang/crates.io-index)" = "ca797db0057bae1a7aa2eef3283a874695455cecf08a43bfb8507ee0ebc1ed69"
 "checksum bitflags 1.2.1 (registry+https://github.com/rust-lang/crates.io-index)" = "cf1de2fe8c75bc145a2f577add951f8134889b4795d47466a54a5c846d691693"
-"checksum c2-chacha 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)" = "214238caa1bf3a496ec3392968969cab8549f96ff30652c9e56885329315f6bb"
 "checksum cc 1.0.50 (registry+https://github.com/rust-lang/crates.io-index)" = "95e28fa049fda1c330bcf9d723be7663a899c4679724b34c81e9f5a326aab8cd"
 "checksum cfg-if 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)" = "4785bdd1c96b2a846b2bd7cc02e86b6b3dbf14e7e53446c4f54c92a361040822"
 "checksum clap 2.33.0 (registry+https://github.com/rust-lang/crates.io-index)" = "5067f5bb2d80ef5d68b4c87db81601f0b75bca627bc2ef76b141d7b846a3c6d9"
-"checksum ctor 0.1.12 (registry+https://github.com/rust-lang/crates.io-index)" = "cd8ce37ad4184ab2ce004c33bf6379185d3b1c95801cab51026bd271bf68eedc"
-"checksum ctrlc 3.1.3 (registry+https://github.com/rust-lang/crates.io-index)" = "c7dfd2d8b4c82121dfdff120f818e09fc4380b0b7e17a742081a89b94853e87f"
-"checksum derivative 1.0.3 (registry+https://github.com/rust-lang/crates.io-index)" = "942ca430eef7a3806595a6737bc388bf51adb888d3fc0dd1b50f1c170167ee3a"
+"checksum ctor 0.1.13 (registry+https://github.com/rust-lang/crates.io-index)" = "47c5e5ac752e18207b12e16b10631ae5f7f68f8805f335f9b817ead83d9ffce1"
+"checksum ctrlc 3.1.4 (registry+https://github.com/rust-lang/crates.io-index)" = "7a4ba686dff9fa4c1c9636ce1010b0cf98ceb421361b0bb3d6faeec43bd217a7"
+"checksum derivative 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)" = "3c6d883546668a3e2011b6a716a7330b82eabb0151b138217f632c8243e17135"
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-"checksum doc-comment 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)" = "923dea538cea0aa3025e8685b20d6ee21ef99c4f77e954a30febbaac5ec73a97"
+"checksum doc-comment 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)" = "807e5847c39ad6a11eac66de492ed1406f76a260eb8656e8740cad9eabc69c27"
 "checksum dotenv 0.15.0 (registry+https://github.com/rust-lang/crates.io-index)" = "77c90badedccf4105eca100756a0b1289e191f6fcbdadd3cee1d2f614f97da8f"
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@@ -604,7 +595,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum vec_map 0.8.1 (registry+https://github.com/rust-lang/crates.io-index)" = "05c78687fb1a80548ae3250346c3db86a80a7cdd77bda190189f2d0a0987c81a"
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-"checksum which 3.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "5475d47078209a02e60614f7ba5e645ef3ed60f771920ac1906d7c1cc65024c8"
+"checksum which 3.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "d011071ae14a2f6671d0b74080ae0cd8ebf3a6f8c9589a2cd45f23126fe29724"
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 "checksum winapi-i686-pc-windows-gnu 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ac3b87c63620426dd9b991e5ce0329eff545bccbbb34f3be09ff6fb6ab51b7b6"
 "checksum winapi-util 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)" = "4ccfbf554c6ad11084fb7517daca16cfdcaccbdadba4fc336f032a8b12c2ad80"
diff --git a/bin/generate-completions b/bin/generate-completions
new file mode 100755
index 00000000..dfcc4de8
--- /dev/null
+++ b/bin/generate-completions
@@ -0,0 +1,8 @@
+#!/usr/bin/env bash
+
+set -euxo pipefail
+
+for script in completions/*; do
+  shell=${script##*.}
+  cargo run -- --completions $shell > $script
+done
diff --git a/completions/just.bash b/completions/just.bash
index 578eb8b6..49f7b25c 100644
--- a/completions/just.bash
+++ b/completions/just.bash
@@ -20,7 +20,7 @@ _just() {
 
     case "${cmd}" in
         just)
-            opts=" -q -v -e -l -h -V -f -d -s  --dry-run --highlight --no-highlight --quiet --clear-shell-args --verbose --dump --edit --evaluate --init --list --summary --help --version --color --justfile --set --shell --shell-arg --working-directory --completions --show  <ARGUMENTS>... "
+            opts=" -q -v -e -l -h -V -f -d -s  --dry-run --highlight --no-highlight --quiet --clear-shell-args --verbose --dump --edit --evaluate --init --list --summary --variables --help --version --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
diff --git a/completions/just.elvish b/completions/just.elvish
index 68089cfb..90f9b03c 100644
--- a/completions/just.elvish
+++ b/completions/just.elvish
@@ -42,6 +42,7 @@ edit:completion:arg-completer[just] = [@words]{
             cand -l 'List available recipes and their arguments'
             cand --list 'List available recipes and their arguments'
             cand --summary 'List names of available recipes'
+            cand --variables 'List names of variables'
             cand -h 'Print help information'
             cand --help 'Print help information'
             cand -V 'Print version information'
diff --git a/completions/just.fish b/completions/just.fish
index 67548ce5..3983a710 100644
--- a/completions/just.fish
+++ b/completions/just.fish
@@ -18,5 +18,6 @@ complete -c just -n "__fish_use_subcommand" -l evaluate -d 'Print evaluated vari
 complete -c just -n "__fish_use_subcommand" -l init -d 'Initialize new justfile in project root'
 complete -c just -n "__fish_use_subcommand" -s l -l list -d 'List available recipes and their arguments'
 complete -c just -n "__fish_use_subcommand" -l summary -d 'List names of available recipes'
+complete -c just -n "__fish_use_subcommand" -l variables -d 'List names of variables'
 complete -c just -n "__fish_use_subcommand" -s h -l help -d 'Print help information'
 complete -c just -n "__fish_use_subcommand" -s V -l version -d 'Print version information'
diff --git a/completions/just.powershell b/completions/just.powershell
index 92f9f8c0..ed790067 100644
--- a/completions/just.powershell
+++ b/completions/just.powershell
@@ -47,6 +47,7 @@ Register-ArgumentCompleter -Native -CommandName 'just' -ScriptBlock {
             [CompletionResult]::new('-l', 'l', [CompletionResultType]::ParameterName, 'List available recipes and their arguments')
             [CompletionResult]::new('--list', 'list', [CompletionResultType]::ParameterName, 'List available recipes and their arguments')
             [CompletionResult]::new('--summary', 'summary', [CompletionResultType]::ParameterName, 'List names of available recipes')
+            [CompletionResult]::new('--variables', 'variables', [CompletionResultType]::ParameterName, 'List names of variables')
             [CompletionResult]::new('-h', 'h', [CompletionResultType]::ParameterName, 'Print help information')
             [CompletionResult]::new('--help', 'help', [CompletionResultType]::ParameterName, 'Print help information')
             [CompletionResult]::new('-V', 'V', [CompletionResultType]::ParameterName, 'Print version information')
diff --git a/completions/just.zsh b/completions/just.zsh
index 7ed88b97..3f5aed21 100644
--- a/completions/just.zsh
+++ b/completions/just.zsh
@@ -42,6 +42,7 @@ _just() {
 '-l[List available recipes and their arguments]' \
 '--list[List available recipes and their arguments]' \
 '--summary[List names of available recipes]' \
+'--variables[List names of variables]' \
 '-h[Print help information]' \
 '--help[Print help information]' \
 '-V[Print version information]' \
diff --git a/justfile b/justfile
index d79dcc57..e9fb1058 100755
--- a/justfile
+++ b/justfile
@@ -157,6 +157,9 @@ watch-readme:
 	just render-readme
 	fswatch -ro README.adoc | xargs -n1 -I{} just render-readme
 
+generate-completions:
+	./bin/generate-completions
+
 # run all polyglot recipes
 polyglot: _python _js _perl _sh _ruby
 # (recipes that start with `_` are hidden from --list)
diff --git a/src/config.rs b/src/config.rs
index 48296bb7..a4137548 100644
--- a/src/config.rs
+++ b/src/config.rs
@@ -23,6 +23,7 @@ pub(crate) struct Config {
 }
 
 mod cmd {
+  pub(crate) const COMPLETIONS: &str = "COMPLETIONS";
   pub(crate) const DUMP: &str = "DUMP";
   pub(crate) const EDIT: &str = "EDIT";
   pub(crate) const EVALUATE: &str = "EVALUATE";
@@ -30,10 +31,30 @@ mod cmd {
   pub(crate) const LIST: &str = "LIST";
   pub(crate) const SHOW: &str = "SHOW";
   pub(crate) const SUMMARY: &str = "SUMMARY";
-  pub(crate) const COMPLETIONS: &str = "COMPLETIONS";
-
-  pub(crate) const ALL: &[&str] = &[COMPLETIONS, DUMP, EDIT, INIT, EVALUATE, LIST, SHOW, SUMMARY];
-  pub(crate) const ARGLESS: &[&str] = &[COMPLETIONS, DUMP, EDIT, INIT, LIST, SHOW, SUMMARY];
+  pub(crate) const VARIABLES: &str = "VARIABLES";
+
+  pub(crate) const ALL: &[&str] = &[
+    COMPLETIONS,
+    DUMP,
+    EDIT,
+    INIT,
+    EVALUATE,
+    LIST,
+    SHOW,
+    SUMMARY,
+    VARIABLES,
+  ];
+
+  pub(crate) const ARGLESS: &[&str] = &[
+    COMPLETIONS,
+    DUMP,
+    EDIT,
+    INIT,
+    LIST,
+    SHOW,
+    SUMMARY,
+    VARIABLES,
+  ];
 }
 
 mod arg {
@@ -206,6 +227,11 @@ impl Config {
           .long("summary")
           .help("List names of available recipes"),
       )
+      .arg(
+        Arg::with_name(cmd::VARIABLES)
+          .long("variables")
+          .help("List names of variables"),
+      )
       .group(ArgGroup::with_name("SUBCOMMAND").args(cmd::ALL));
 
     if cfg!(feature = "help4help2man") {
@@ -345,6 +371,8 @@ impl Config {
         });
       }
       Subcommand::Evaluate { overrides }
+    } else if matches.is_present(cmd::VARIABLES) {
+      Subcommand::Variables
     } else {
       Subcommand::Run {
         arguments: positional.arguments,
@@ -419,13 +447,14 @@ impl Config {
     match &self.subcommand {
       Dump => Self::dump(justfile),
       Evaluate { overrides } => self.run(justfile, &search, overrides, &Vec::new()),
+      List => self.list(justfile),
       Run {
         arguments,
         overrides,
       } => self.run(justfile, &search, overrides, arguments),
-      List => self.list(justfile),
       Show { ref name } => Self::show(&name, justfile),
       Summary => Self::summary(justfile),
+      Variables => Self::variables(justfile),
       Completions { .. } | Edit | Init => unreachable!(),
     }
   }
@@ -635,6 +664,17 @@ impl Config {
     }
     Ok(())
   }
+
+  fn variables(justfile: Justfile) -> Result<(), i32> {
+    for (i, (_, assignment)) in justfile.assignments.iter().enumerate() {
+      if i > 0 {
+        print!(" ");
+      }
+      print!("{}", assignment.name)
+    }
+    println!();
+    Ok(())
+  }
 }
 
 #[cfg(test)]
@@ -668,6 +708,7 @@ FLAGS:
         --no-highlight        Don't highlight echoed recipe lines in bold
     -q, --quiet               Suppress all output
         --summary             List names of available recipes
+        --variables           List names of variables
     -v, --verbose             Use verbose output
 
 OPTIONS:
diff --git a/src/subcommand.rs b/src/subcommand.rs
index 664842e3..82b9c962 100644
--- a/src/subcommand.rs
+++ b/src/subcommand.rs
@@ -20,4 +20,5 @@ pub(crate) enum Subcommand {
     name: String,
   },
   Summary,
+  Variables,
 }


Test patch:
diff --git a/tests/integration.rs b/tests/integration.rs
index 7a2ebf9b..6ed38b86 100644
--- a/tests/integration.rs
+++ b/tests/integration.rs
@@ -2459,3 +2459,15 @@ test! {
   status: EXIT_SUCCESS,
   shell: false,
 }
+
+test! {
+  name: variables,
+  justfile: "
+    z := 'a'
+    a := 'z'
+  ",
+  args: ("--variables"),
+  stdout: "a z\n",
+  stderr: "",
+  shell: false,
+}