sq: add command output-versions

This allows the user to query what output versions are available and
what is the current default one.

Sponsored-by: NLnet Foundation; NGI Assure

4 files changed, 64 insertions, 4 deletions

diff --git a/sq/sq-usage.md b/sq/sq-usage.md
index 85e8d7c2..927c66a3 100644
--- a/sq/sq-usage.md
+++ b/sq/sq-usage.md
@@ -32,7 +32,10 @@ OPTIONS:
             [possible values: human-readable, json]
 
         --output-version <VERSION>
-            Produces output variant VERSION
+            Produces output variant VERSION, such as 0.0.0. The default is the
+            newest version. The output version is separate from the version of
+            the sq program. To see the current supported versions, use
+            output-versions subcommand.
 
             [env: SQ_OUTPUT_VERSION=]
 
@@ -80,6 +83,8 @@ SUBCOMMANDS:
             Generates revocation certificates
     help
             Print this message or the help of the given subcommand(s)
+    output-versions
+            List supported output versions
 ```
 
 ## Subcommand sq encrypt
@@ -2140,3 +2145,19 @@ OPTIONS:
             Chooses keys valid at the specified time and sets the revocation
             certificate's creation time
 ```
+
+## Subcommand sq output versions
+
+```text
+List supported output versions
+
+USAGE:
+    sq output-versions [OPTIONS]
+
+OPTIONS:
+        --default
+            List only the default output version
+
+    -h, --help
+            Print help information
+```
diff --git a/sq/src/output.rs b/sq/src/output.rs
index eb7f5f55..811bc07d 100644
--- a/sq/src/output.rs
+++ b/sq/src/output.rs
@@ -13,6 +13,9 @@ use serde::Serialize;
 pub use keyring::ListItem as KeyringListItem;
 pub use wkd::WkdUrlVariant;
 
+pub const DEFAULT_OUTPUT_VERSION: OutputVersion = OutputVersion::new(0, 0, 0);
+pub const OUTPUT_VERSIONS: &[OutputVersion] = &[OutputVersion::new(0, 0, 0)];
+
 /// What output format to prefer, when there's an option?
 #[derive(Clone)]
 pub enum OutputFormat {
@@ -98,6 +101,14 @@ impl fmt::Display for OutputVersion {
     }
 }
 
+impl PartialEq<OutputVersion> for &OutputVersion {
+    fn eq(&self, other: &OutputVersion) -> bool {
+        self.major == other.major &&
+            self.minor == other.minor &&
+            self.patch == other.patch
+    }
+}
+
 fn parse_ints(s: &str) -> Result<Vec<usize>> {
     let mut ints = vec![];
     let mut v = s;
@@ -134,10 +145,9 @@ pub enum Model {
 }
 
 impl Model {
-    const DEFAULT_VERSION: OutputVersion = OutputVersion::new(0, 0, 0);
 
     fn version(v: Option<OutputVersion>) -> OutputVersion {
-        v.unwrap_or(Self::DEFAULT_VERSION)
+        v.unwrap_or(DEFAULT_OUTPUT_VERSION)
     }
 
     /// Create a model for the output of `sq wkd url` and `sq wkd
diff --git a/sq/src/sq.rs b/sq/src/sq.rs
index bf761f41..e5ba9860 100644
--- a/sq/src/sq.rs
+++ b/sq/src/sq.rs
@@ -418,6 +418,16 @@ fn main() -> Result<()> {
     };
 
     match c.subcommand {
+        SqSubcommands::OutputVersions(command) => {
+            if command.default {
+                println!("{}", output::DEFAULT_OUTPUT_VERSION);
+            } else {
+                for v in output::OUTPUT_VERSIONS {
+                    println!("{}", v);
+                }
+            }
+        }
+
         SqSubcommands::Decrypt(command) => {
 
             let mut input = open_or_stdin(command.io.input.as_deref())?;
diff --git a/sq/src/sq_cli.rs b/sq/src/sq_cli.rs
index 123f428c..aff78c71 100644
--- a/sq/src/sq_cli.rs
+++ b/sq/src/sq_cli.rs
@@ -64,7 +64,12 @@ pub struct SqCommand {
         long = "output-version",
         value_name = "VERSION",
         env = "SQ_OUTPUT_VERSION",
-        help = "Produces output variant VERSION",
+        help = "Produces output variant VERSION.",
+        long_help = "Produces output variant VERSION, such as 0.0.0. \
+                     The default is the newest version. The output version \
+                     is separate from the version of the sq program. To see \
+                     the current supported versions, use output-versions \
+                     subcommand."
     )]
     pub output_version: Option<String>,
     #[clap(
@@ -117,6 +122,8 @@ pub enum SqSubcommands {
     Packet(PacketCommand),
 
     Revoke(RevokeCommand),
+
+    OutputVersions(OutputVersionsCommand),
 }
 
 use chrono::{offset::Utc, DateTime};
@@ -2807,6 +2814,18 @@ impl<'a> std::fmt::Display for CliSessionKeyDisplay<'a> {
     }
 }
 
+#[derive(Parser, Debug)]
+#[clap(
+    name = "output-versions",
+    display_order = 110,
+    about = "List supported output versions",
+)]
+pub struct OutputVersionsCommand {
+    /// List only the default output version.
+    #[clap(long)]
+    pub default: bool,
+}
+
 #[cfg(feature = "autocrypt")]
 pub mod autocrypt {
     use super::*;