switch from ancient clap/structopt release to bpaf

Improves #70: this reduces binary size from 12.3 MiB to 11.9 MiB (3%) on
macOS/arm64.

The user experience is almost the same. (The help output's `Usage:`
lines lack the e.g. `moonfire-nvr run` prefix of argv[0] and subcommand,
which isn't ideal, but I guess it's pretty minor in the grand scheme of
things.)

server/Cargo.lock

@@ -47,15 +47,6 @@ dependencies = [
  "libc",
 ]
 
-[[package]]
-name = "ansi_term"
-version = "0.12.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d52a9bb7ec0cf484c551830a7ce27bd20d67eac647e1befb56b0be4ee39a55d2"
-dependencies = [
- "winapi",
-]
-
 [[package]]
 name = "anyhow"
 version = "1.0.68"
@@ -153,6 +144,27 @@ dependencies = [
  "generic-array",
 ]
 
+[[package]]
+name = "bpaf"
+version = "0.7.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "863c0b21775e45ebf9bbb3a6d0cd9b3421c88a036e825359e3d4015561f3e23c"
+dependencies = [
+ "bpaf_derive",
+ "owo-colors",
+]
+
+[[package]]
+name = "bpaf_derive"
+version = "0.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5ed63113bfb3a9bb25dd131acdf0044c7404000ea57dd9eec1f221e3547b4748"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "bstr"
 version = "1.1.0"
@@ -220,20 +232,6 @@ dependencies = [
  "inout",
 ]
 
-[[package]]
-name = "clap"
-version = "2.34.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a0610544180c38b88101fecf2dd634b174a62eef6946f84dfc6a7127512b381c"
-dependencies = [
- "ansi_term",
- "atty",
- "bitflags",
- "term_size",
- "textwrap",
- "unicode-width",
-]
-
 [[package]]
 name = "codespan-reporting"
 version = "0.11.1"
@@ -756,15 +754,6 @@ dependencies = [
  "hashbrown 0.13.1",
 ]
 
-[[package]]
-name = "heck"
-version = "0.3.3"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6d621efb26863f0e9924c6ac577e8275e5e6b77455db64ffa6c65c904e9e132c"
-dependencies = [
- "unicode-segmentation",
-]
-
 [[package]]
 name = "hermit-abi"
 version = "0.1.19"
@@ -974,6 +963,12 @@ version = "2.7.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "11b0d96e660696543b251e58030cf9787df56da39dab19ad60eae7353040917e"
 
+[[package]]
+name = "is_ci"
+version = "1.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "616cde7c720bb2bb5824a224687d8f77bfd38922027f01d825cd7453be5099fb"
+
 [[package]]
 name = "itertools"
 version = "0.10.5"
@@ -1163,9 +1158,9 @@ version = "0.7.5"
 dependencies = [
  "base64",
  "blake3",
+ "bpaf",
  "byteorder",
  "bytes",
- "clap",
  "cursive",
  "failure",
  "fnv",
@@ -1196,7 +1191,6 @@ dependencies = [
  "serde",
  "serde_json",
  "smallvec",
- "structopt",
  "sync_wrapper",
  "tempfile",
  "time 0.1.45",
@@ -1412,6 +1406,15 @@ dependencies = [
  "stable_deref_trait",
 ]
 
+[[package]]
+name = "owo-colors"
+version = "3.5.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c1b04fb49957986fdce4d6ee7a65027d55d4b6d2265e5848bbb507b58ccfdb6f"
+dependencies = [
+ "supports-color",
+]
+
 [[package]]
 name = "password-hash"
 version = "0.4.2"
@@ -1488,30 +1491,6 @@ version = "0.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c6fa0831dd7cc608c38a5e323422a0077678fa5744aa2be4ad91c4ece8eec8d5"
 
-[[package]]
-name = "proc-macro-error"
-version = "1.0.4"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "da25490ff9892aab3fcf7c36f08cfb902dd3e71ca0f9f9517bea02a73a5ce38c"
-dependencies = [
- "proc-macro-error-attr",
- "proc-macro2",
- "quote",
- "syn",
- "version_check",
-]
-
-[[package]]
-name = "proc-macro-error-attr"
-version = "1.0.4"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a1be40180e52ecc98ad80b184934baf3d0d29f979574e439af5a55274b35f869"
-dependencies = [
- "proc-macro2",
- "quote",
- "version_check",
-]
-
 [[package]]
 name = "proc-macro2"
 version = "1.0.49"
@@ -1967,36 +1946,22 @@ version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a2eb9349b6444b326872e140eb1cf5e7c522154d69e7a0ffb0fb81c06b37543f"
 
-[[package]]
-name = "structopt"
-version = "0.3.26"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0c6b5c64445ba8094a6ab0c3cd2ad323e07171012d9c98b0b15651daf1787a10"
-dependencies = [
- "clap",
- "lazy_static",
- "structopt-derive",
-]
-
-[[package]]
-name = "structopt-derive"
-version = "0.4.18"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "dcb5ae327f9cc13b68763b5749770cb9e048a99bd9dfdfa58d0cf05d5f64afe0"
-dependencies = [
- "heck",
- "proc-macro-error",
- "proc-macro2",
- "quote",
- "syn",
-]
-
 [[package]]
 name = "subtle"
 version = "2.4.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6bdef32e8150c2a081110b42772ffe7d7c9032b606bc226c8260fd97e0976601"
 
+[[package]]
+name = "supports-color"
+version = "1.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8ba6faf2ca7ee42fdd458f4347ae0a9bd6bcc445ad7cb57ad82b383f18870d6f"
+dependencies = [
+ "atty",
+ "is_ci",
+]
+
 [[package]]
 name = "syn"
 version = "1.0.107"
@@ -2059,16 +2024,6 @@ dependencies = [
  "winapi-util",
 ]
 
-[[package]]
-name = "textwrap"
-version = "0.11.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d326610f408c7a4eb6f51c37c330e496b08506c9457c9d34287ecc38809fb060"
-dependencies = [
- "term_size",
- "unicode-width",
-]
-
 [[package]]
 name = "thiserror"
 version = "1.0.38"

server/Cargo.toml

@@ -2,7 +2,7 @@
 name = "moonfire-nvr"
 version = "0.7.5"
 authors = ["Scott Lamb <slamb@slamb.org>"]
-edition = "2018"
+edition = "2021"
 resolver = "2"
 license-file = "../LICENSE.txt"
 rust-version = "1.64"
@@ -24,9 +24,9 @@ members = ["base", "db"]
 base = { package = "moonfire-base", path = "base" }
 base64 = "0.13.0"
 blake3 = "1.0.0"
+bpaf = { version = "0.7.8", features = ["autocomplete", "bright-color", "derive"] }
 bytes = "1"
 byteorder = "1.0"
-clap = { version = "2.33.3", default-features = false, features = ["color", "wrap_help"] }
 cursive = "0.20.0"
 db = { package = "moonfire-db", path = "db" }
 failure = "0.1.1"
@@ -53,7 +53,6 @@ rusqlite = "0.28.0"
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0"
 smallvec = { version = "1.7", features = ["union"] }
-structopt = { version = "0.3.13", default-features = false }
 sync_wrapper = "0.1.0"
 time = "0.1"
 tokio = { version = "1.24", features = ["macros", "rt-multi-thread", "signal", "sync", "time"] }

server/src/cmds/check.rs

@@ -4,45 +4,39 @@
 
 //! Subcommand to check the database and sample file dir for errors.
 
+use bpaf::Bpaf;
 use db::check;
 use failure::Error;
 use std::path::PathBuf;
-use structopt::StructOpt;
 
-#[derive(StructOpt)]
+#[derive(Bpaf, Debug)]
 pub struct Args {
     /// Directory holding the SQLite3 index database.
-    #[structopt(
+    ///
-        long,
+    /// default: `/var/lib/moonfire-nvr/db`.
-        default_value = "/var/lib/moonfire-nvr/db",
+    #[bpaf(argument("PATH"), fallback_with(crate::default_db_dir))]
-        value_name = "path",
-        parse(from_os_str)
-    )]
     db_dir: PathBuf,
 
-    /// Compare sample file lengths on disk to the database.
+    /// Compares sample file lengths on disk to the database.
-    #[structopt(long)]
     compare_lens: bool,
 
-    /// Trash sample files without matching recording rows in the database.
+    /// Trashes sample files without matching recording rows in the database.
-    /// This addresses "Missing ... row" errors.
+    /// This addresses `Missing ... row` errors.
     ///
-    /// The ids are added to the "garbage" table to indicate the files need to
+    /// The ids are added to the `garbage` table to indicate the files need to
     /// be deleted. Garbage is collected on normal startup.
-    #[structopt(long)]
     trash_orphan_sample_files: bool,
 
-    /// Delete recording rows in the database without matching sample files.
+    /// Deletes recording rows in the database without matching sample files.
-    /// This addresses "Recording ... missing file" errors.
+    ///
-    #[structopt(long)]
+    /// This addresses `Recording ... missing file` errors.
     delete_orphan_rows: bool,
 
-    /// Trash recordings when their database rows appear corrupt.
+    /// Trashes recordings when their database rows appear corrupt.
     /// This addresses "bad video_index" errors.
     ///
-    /// The ids are added to the "garbage" table to indicate their files need to
+    /// The ids are added to the `garbage` table to indicate their files need to
     /// be deleted. Garbage is collected on normal startup.
-    #[structopt(long)]
     trash_corrupt_rows: bool,
 }
 

server/src/cmds/config/mod.rs

@@ -8,26 +8,23 @@
 //! configuration will likely be almost entirely done through a web-based UI.
 
 use base::clock;
+use bpaf::Bpaf;
 use cursive::views;
 use cursive::Cursive;
 use failure::Error;
 use std::path::PathBuf;
 use std::sync::Arc;
-use structopt::StructOpt;
 
 mod cameras;
 mod dirs;
 mod users;
 
-#[derive(StructOpt)]
+#[derive(Bpaf, Debug)]
 pub struct Args {
     /// Directory holding the SQLite3 index database.
-    #[structopt(
+    ///
-        long,
+    /// default: `/var/lib/moonfire-nvr/db`.
-        default_value = "/var/lib/moonfire-nvr/db",
+    #[bpaf(argument("PATH"), fallback_with(crate::default_db_dir))]
-        value_name = "path",
-        parse(from_os_str)
-    )]
     db_dir: PathBuf,
 }
 

server/src/cmds/init.rs

@@ -2,20 +2,17 @@
 // Copyright (C) 2020 The Moonfire NVR Authors; see AUTHORS and LICENSE.txt.
 // SPDX-License-Identifier: GPL-v3.0-or-later WITH GPL-3.0-linking-exception.
 
+use bpaf::Bpaf;
 use failure::Error;
 use log::info;
 use std::path::PathBuf;
-use structopt::StructOpt;
 
-#[derive(StructOpt)]
+#[derive(Bpaf, Debug)]
 pub struct Args {
     /// Directory holding the SQLite3 index database.
-    #[structopt(
+    ///
-        long,
+    /// default: `/var/lib/moonfire-nvr/db`.
-        default_value = "/var/lib/moonfire-nvr/db",
+    #[bpaf(argument("PATH"), fallback_with(crate::default_db_dir))]
-        value_name = "path",
-        parse(from_os_str)
-    )]
     db_dir: PathBuf,
 }
 

server/src/cmds/login.rs

@@ -5,51 +5,58 @@
 //! Subcommand to login a user (without requiring a password).
 
 use base::clock::{self, Clocks};
+use bpaf::Bpaf;
 use db::auth::SessionFlag;
 use failure::{format_err, Error};
 use std::io::Write as _;
 use std::os::unix::fs::OpenOptionsExt as _;
 use std::path::PathBuf;
-use structopt::StructOpt;
+use std::str::FromStr;
 
-#[derive(Debug, Default, StructOpt)]
+fn parse_perms(perms: String) -> Result<db::Permissions, protobuf::text_format::ParseError> {
+    protobuf::text_format::parse_from_str(&perms)
+}
+
+fn parse_flags(flags: String) -> Result<Vec<SessionFlag>, Error> {
+    flags.split(',').map(SessionFlag::from_str).collect()
+}
+
+#[derive(Bpaf, Debug)]
 pub struct Args {
     /// Directory holding the SQLite3 index database.
-    #[structopt(
+    ///
-        long,
+    /// default: `/var/lib/moonfire-nvr/db`.
-        default_value = "/var/lib/moonfire-nvr/db",
+    #[bpaf(argument("PATH"), fallback_with(crate::default_db_dir))]
-        value_name = "path",
-        parse(from_os_str)
-    )]
     db_dir: PathBuf,
 
-    /// Create a session with the given permissions.
+    /// Creates a session with the given permissions.
     ///
     /// If unspecified, uses user's default permissions.
-    #[structopt(long, value_name="perms",
+    #[bpaf(argument::<String>("PERMS"), parse(parse_perms), optional)]
-                parse(try_from_str = protobuf::text_format::parse_from_str))]
     permissions: Option<db::Permissions>,
 
-    /// Restrict this cookie to the given domain.
+    /// Restricts this cookie to the given domain.
-    #[structopt(long)]
+    #[bpaf(argument("DOMAIN"))]
     domain: Option<String>,
 
-    /// Write the cookie to a new curl-compatible cookie-jar file.
+    /// Writes the cookie to a new curl-compatible cookie-jar file.
     ///
-    /// ---domain must be specified. This file can be used later with curl's --cookie flag.
+    /// `--domain` must be specified. This file can be used later with curl's `--cookie` flag.
-    #[structopt(long, requires("domain"), value_name = "path")]
+    #[bpaf(argument("PATH"))]
     curl_cookie_jar: Option<PathBuf>,
 
-    /// Set the given db::auth::SessionFlags.
+    /// Sets the given db::auth::SessionFlags.
-    #[structopt(
+    ///
-        long,
+    /// default: `http-only,secure,same-site,same-site-strict`.
-        default_value = "http-only,secure,same-site,same-site-strict",
+    #[bpaf(
-        value_name = "flags",
+        argument::<String>("FLAGS"),
-        use_delimiter = true
+        fallback_with(|| Ok::<_, std::convert::Infallible>("http-only,secure,same-site,same-site-strict".to_owned())),
+        parse(parse_flags),
     )]
     session_flags: Vec<SessionFlag>,
 
     /// Create the session for this username.
+    #[bpaf(argument("USERNAME"))]
     username: String,
 }
 
@@ -87,7 +94,7 @@ pub fn run(args: Args) -> Result<i32, Error> {
         let d = args
             .domain
             .as_ref()
-            .ok_or_else(|| format_err!("--cookiejar requires --domain"))?;
+            .ok_or_else(|| format_err!("--curl-cookie-jar requires --domain"))?;
         let mut f = std::fs::OpenOptions::new()
             .write(true)
             .create_new(true)

server/src/cmds/run/config.rs

@@ -27,6 +27,9 @@ pub struct ConfigFile {
     pub binds: Vec<BindConfig>,
 
     /// Directory holding the SQLite3 index database.
+    ///
+    ///
+    /// default: `/var/lib/moonfire-nvr/db`.
     #[serde(default = "default_db_dir")]
     pub db_dir: PathBuf,
 

server/src/cmds/run/mod.rs

@@ -6,6 +6,7 @@ use crate::streamer;
 use crate::web;
 use crate::web::accept::Listener;
 use base::clock;
+use bpaf::Bpaf;
 use db::{dir, writer};
 use failure::{bail, Error, ResultExt};
 use fnv::FnvHashMap;
@@ -18,23 +19,24 @@ use std::path::Path;
 use std::path::PathBuf;
 use std::sync::Arc;
 use std::thread;
-use structopt::StructOpt;
 use tokio::signal::unix::{signal, SignalKind};
 
 use self::config::ConfigFile;
 
 mod config;
 
-#[derive(StructOpt)]
+#[derive(Bpaf, Debug)]
 pub struct Args {
-    #[structopt(short, long, default_value = "/etc/moonfire-nvr.toml")]
+    /// Path to configuration file.
+    ///
+    /// default: `/etc/moonfire-nvr.toml`. See `ref/config.md` for config file documentation.
+    #[bpaf(short, long, argument("PATH"), fallback_with(|| Ok::<_, Error>("/etc/moonfire-nvr.toml".into())))]
     config: PathBuf,
 
-    /// Open the database in read-only mode and disables recording.
+    /// Opens the database in read-only mode and disables recording.
     ///
     /// Note this is incompatible with session authentication; consider adding
-    /// a bind with `allow_unauthenticated_permissions` to your config.
+    /// a bind with `allowUnauthenticatedPermissions` to your config.
-    #[structopt(long)]
     read_only: bool,
 }
 

server/src/cmds/sql.rs

@@ -5,35 +5,31 @@
 //! Subcommand to run a SQLite shell.
 
 use super::OpenMode;
+use bpaf::Bpaf;
 use failure::Error;
 use std::ffi::OsString;
 use std::os::unix::process::CommandExt;
 use std::path::PathBuf;
 use std::process::Command;
-use structopt::StructOpt;
 
-#[derive(StructOpt)]
+#[derive(Bpaf, Debug, PartialEq, Eq)]
 pub struct Args {
     /// Directory holding the SQLite3 index database.
-    #[structopt(
+    ///
-        long,
+    /// default: `/var/lib/moonfire-nvr/db`.
-        default_value = "/var/lib/moonfire-nvr/db",
+    #[bpaf(fallback_with(crate::default_db_dir))]
-        value_name = "path",
-        parse(from_os_str)
-    )]
     db_dir: PathBuf,
 
     /// Opens the database in read-only mode and locks it only for shared access.
     ///
-    /// This can be run simultaneously with "moonfire-nvr run --read-only".
+    /// This can be run simultaneously with `moonfire-nvr run --read-only`.
-    #[structopt(long)]
     read_only: bool,
 
     /// Arguments to pass to sqlite3.
     ///
-    /// Use the -- separator to pass sqlite3 options, as in
+    /// Use the `--` separator to pass sqlite3 options, as in
-    /// "moonfire-nvr sql -- -line 'select username from user'".
+    /// `moonfire-nvr sql -- -line 'select username from user'`.
-    #[structopt(parse(from_os_str))]
+    #[bpaf(positional)]
     arg: Vec<OsString>,
 }
 
@@ -58,3 +54,32 @@ pub fn run(args: Args) -> Result<i32, Error> {
         .exec()
         .into())
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    use bpaf::Parser;
+
+    #[test]
+    fn parse_args() {
+        let args = args()
+            .to_options()
+            .run_inner(bpaf::Args::from(&[
+                "--db-dir",
+                "/foo/bar",
+                "--",
+                "-line",
+                "select username from user",
+            ]))
+            .unwrap();
+        assert_eq!(
+            args,
+            Args {
+                db_dir: "/foo/bar".into(),
+                read_only: false, // default
+                arg: vec!["-line".into(), "select username from user".into()],
+            }
+        );
+    }
+}

server/src/cmds/ts.rs

@@ -2,18 +2,18 @@
 // Copyright (C) 2020 The Moonfire NVR Authors; see AUTHORS and LICENSE.txt.
 // SPDX-License-Identifier: GPL-v3.0-or-later WITH GPL-3.0-linking-exception.
 
+use bpaf::Bpaf;
 use failure::Error;
-use structopt::StructOpt;
 
-#[derive(StructOpt)]
+#[derive(Bpaf, Debug)]
 pub struct Args {
     /// Timestamp(s) to translate.
     ///
     /// May be either an integer or an RFC-3339-like string:
     /// `YYYY-mm-dd[THH:MM[:SS[:FFFFF]]][{Z,{+,-,}HH:MM}]`.
     ///
-    /// Eg: `142913484000000`, `2020-04-26`, `2020-04-26T12:00:00:00000-07:00`.
+    /// E.g.: `142913484000000`, `2020-04-26`, `2020-04-26T12:00:00:00000-07:00`.
-    #[structopt(required = true)]
+    #[bpaf(positional("TS"), some("must specify at least one timestamp"))]
     timestamps: Vec<String>,
 }
 

server/src/cmds/upgrade/mod.rs

@@ -2,41 +2,36 @@
 // Copyright (C) 2020 The Moonfire NVR Authors; see AUTHORS and LICENSE.txt.
 // SPDX-License-Identifier: GPL-v3.0-or-later WITH GPL-3.0-linking-exception.
 
+use bpaf::Bpaf;
 /// Upgrades the database schema.
 ///
 /// See `guide/schema.md` for more information.
 use failure::Error;
-use structopt::StructOpt;
 
-#[derive(StructOpt)]
+#[derive(Bpaf, Debug)]
 pub struct Args {
-    #[structopt(
+    /// Directory holding the SQLite3 index database.
-        long,
+    ///
-        help = "Directory holding the SQLite3 index database.",
+    ///
-        default_value = "/var/lib/moonfire-nvr/db",
+    /// default: `/var/lib/moonfire-nvr/db`.
-        parse(from_os_str)
+    #[bpaf(argument("PATH"), fallback_with(crate::default_db_dir))]
-    )]
     db_dir: std::path::PathBuf,
 
-    #[structopt(
+    /// When upgrading from schema version 1 to 2, the sample file directory.
-        help = "When upgrading from schema version 1 to 2, the sample file directory.",
+    #[bpaf(argument("PATH"))]
-        long,
-        parse(from_os_str)
-    )]
     sample_file_dir: Option<std::path::PathBuf>,
 
-    #[structopt(
+    /// Resets the SQLite journal_mode to the specified mode prior to
-        help = "Resets the SQLite journal_mode to the specified mode prior to \
+    /// the upgrade.
-               the upgrade. The default, delete, is recommended. off is very \
+    ///
-               dangerous but may be desirable in some circumstances. See \
+    ///
-               guide/schema.md for more information. The journal mode will be \
+    /// default: `delete` (recommended). `off` is very dangerous but may be
-               reset to wal after the upgrade.",
+    /// desirable in some circumstances. See `guide/schema.md` for more
-        long,
+    /// information. The journal mode will be reset to `wal` after the upgrade.
-        default_value = "delete"
+    #[bpaf(argument("MODE"), fallback_with(|| Ok::<_, std::convert::Infallible>("delete".into())))]
-    )]
     preset_journal: String,
 
-    #[structopt(help = "Skips the normal post-upgrade vacuum operation.", long)]
+    /// Skips the normal post-upgrade vacuum operation.
     no_vacuum: bool,
 }
 

server/src/main.rs

@@ -4,10 +4,10 @@
 
 #![cfg_attr(all(feature = "nightly", test), feature(test))]
 
+use bpaf::Bpaf;
 use log::{debug, error};
 use std::fmt::Write;
 use std::str::FromStr;
-use structopt::StructOpt;
 
 mod body;
 mod cmds;
@@ -19,43 +19,50 @@ mod stream;
 mod streamer;
 mod web;
 
-#[derive(StructOpt)]
+/// Moonfire NVR: security camera network video recorder.
-#[structopt(
+#[derive(Bpaf, Debug)]
-    name = "moonfire-nvr",
+#[bpaf(options, version)]
-    about = "security camera network video recorder",
-    global_settings(&[clap::AppSettings::ColoredHelp])
-)]
 enum Args {
     /// Checks database integrity (like fsck).
-    Check(cmds::check::Args),
+    #[bpaf(command)]
+    Check(#[bpaf(external(cmds::check::args))] cmds::check::Args),
 
     /// Interactively edits configuration.
-    Config(cmds::config::Args),
+    #[bpaf(command)]
+    Config(#[bpaf(external(cmds::config::args))] cmds::config::Args),
 
     /// Initializes a database.
-    Init(cmds::init::Args),
+    #[bpaf(command)]
+    Init(#[bpaf(external(cmds::init::args))] cmds::init::Args),
 
     /// Logs in a user, returning the session cookie.
     ///
+    ///
     /// This is a privileged command that directly accesses the database. It doesn't check the
     /// user's password and even can be used to create sessions with permissions the user doesn't
     /// have.
-    Login(cmds::login::Args),
+    #[bpaf(command)]
+    Login(#[bpaf(external(cmds::login::args))] cmds::login::Args),
 
     /// Runs the server, saving recordings and allowing web access.
-    Run(cmds::run::Args),
+    #[bpaf(command)]
+    Run(#[bpaf(external(cmds::run::args))] cmds::run::Args),
 
     /// Runs a SQLite3 shell on Moonfire NVR's index database.
     ///
+    ///
     /// Note this locks the database to prevent simultaneous access with a running server. The
     /// server maintains cached state which could be invalidated otherwise.
-    Sql(cmds::sql::Args),
+    #[bpaf(command)]
+    Sql(#[bpaf(external(cmds::sql::args))] cmds::sql::Args),
 
     /// Translates between integer and human-readable timestamps.
-    Ts(cmds::ts::Args),
+    #[bpaf(command)]
+    Ts(#[bpaf(external(cmds::ts::args))] cmds::ts::Args),
 
     /// Upgrades to the latest database schema.
-    Upgrade(cmds::upgrade::Args),
+    #[bpaf(command)]
+    Upgrade(#[bpaf(external(cmds::upgrade::args))] cmds::upgrade::Args),
 }
 
 impl Args {
@@ -73,6 +80,11 @@ impl Args {
     }
 }
 
+/// Returns the default database dir, for use in argument parsing with `bpaf(fallback_with(...))`.
+fn default_db_dir() -> Result<std::path::PathBuf, std::convert::Infallible> {
+    Ok("/var/lib/moonfire-nvr/db".into())
+}
+
 /// Custom panic hook that logs instead of directly writing to stderr.
 ///
 /// This means it includes a timestamp and is more recognizable as a serious
@@ -112,7 +124,6 @@ fn main() {
         std::process::exit(1);
     }
 
-    let args = Args::from_args();
     let mut h = mylog::Builder::new()
         .set_format(
             ::std::env::var("MOONFIRE_FORMAT")
@@ -130,6 +141,22 @@ fn main() {
         .build();
     h.clone().install().unwrap();
 
+    // TODO: remove this when bpaf adds more direct support for defaulting to `--help`.
+    // See discussion: <https://github.com/pacak/bpaf/discussions/165>.
+    if std::env::args_os().len() < 2 {
+        match args().run_inner(bpaf::Args::from(&["--help"])) {
+            Ok(a) => panic!("bpaf --help should not return Ok: {a:#?}"),
+            Err(bpaf::ParseFailure::Stdout(msg)) => {
+                print!("{msg}");
+                std::process::exit(0);
+            }
+            Err(bpaf::ParseFailure::Stderr(msg)) => {
+                eprint!("{msg}");
+                std::process::exit(1);
+            }
+        }
+    }
+
     let use_panic_hook = ::std::env::var("MOONFIRE_PANIC_HOOK")
         .map(|s| s != "false" && s != "0")
         .unwrap_or(true);
@@ -137,6 +164,9 @@ fn main() {
         std::panic::set_hook(Box::new(&panic_hook));
     }
 
+    let args = args().run();
+    log::trace!("Parsed command-line arguments: {args:#?}");
+
     let r = {
         let _a = h.async_scope();
         args.run()
@@ -152,3 +182,11 @@ fn main() {
         }
     }
 }
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn bpaf_invariants() {
+        super::args().check_invariants(false);
+    }
+}