overhaul error messages

Inspired by the poor error message here:
https://github.com/scottlamb/moonfire-nvr/issues/107#issuecomment-777587727

*   print the friendlier Display version of the error rather than Debug.
    Eg, "EROFS: Read-only filesystem" rather than "Sys(EROFS)". Do this
    everywhere: on command exit, on syncer retries, and on stream
    retries.
*   print the most immediate problem and additional lines for each
    cause.
*   print the backtrace or an advertisement for RUST_BACKTRACE=1 if it's
    unavailable.
*   also mention RUST_BACKTRACE=1 in the troubleshooting guide.
*   add context in various places, including pathnames. There are surely
    many places more it'd be helpful, but this is a start.
*   allow subcommands to return failure without an Error.
    In particular, "moonfire-nvr check" does its own error printing
    because it wants to print all the errors it finds. Printing "see
    earlier errors" with a meaningless stack trace seems like it'd just
    confuse. But I also want to get rid of the misleading "Success" at
    the end and 0 return to the OS.

server/src/cmds/check.rs

@@ -47,7 +47,7 @@ pub struct Args {
     compare_lens: bool,
 }
 
-pub fn run(args: &Args) -> Result<(), Error> {
+pub fn run(args: &Args) -> Result<i32, Error> {
     // TODO: ReadOnly should be sufficient but seems to fail.
     let (_db_dir, conn) = super::open_conn(&args.db_dir, super::OpenMode::ReadWrite)?;
     check::run(&conn, &check::Options {

server/src/cmds/config/mod.rs

@@ -54,7 +54,7 @@ pub struct Args {
     db_dir: PathBuf,
 }
 
-pub fn run(args: &Args) -> Result<(), Error> {
+pub fn run(args: &Args) -> Result<i32, Error> {
     let (_db_dir, conn) = super::open_conn(&args.db_dir, super::OpenMode::ReadWrite)?;
     let clocks = clock::RealClocks {};
     let db = Arc::new(db::Database::new(clocks, conn, true)?);
@@ -77,5 +77,5 @@ pub fn run(args: &Args) -> Result<(), Error> {
 
     siv.run();
 
-    Ok(())
+    Ok(0)
 }

server/src/cmds/init.rs

@@ -41,14 +41,14 @@ pub struct Args {
     db_dir: PathBuf,
 }
 
-pub fn run(args: &Args) -> Result<(), Error> {
+pub fn run(args: &Args) -> Result<i32, Error> {
     let (_db_dir, mut conn) = super::open_conn(&args.db_dir, super::OpenMode::Create)?;
 
     // Check if the database has already been initialized.
     let cur_ver = db::get_schema_version(&conn)?;
     if let Some(v) = cur_ver {
         info!("Database is already initialized with schema version {}.", v);
-        return Ok(());
+        return Ok(0);
     }
 
     // Use WAL mode (which is the most efficient way to preserve database integrity) with a large
@@ -63,5 +63,5 @@ pub fn run(args: &Args) -> Result<(), Error> {
     "#)?;
     db::init(&mut conn)?;
     info!("Database initialized.");
-    Ok(())
+    Ok(0)
 }

server/src/cmds/login.rs

@@ -71,7 +71,7 @@ pub struct Args {
     username: String,
 }
 
-pub fn run(args: &Args) -> Result<(), Error> {
+pub fn run(args: &Args) -> Result<i32, Error> {
     let clocks = clock::RealClocks {};
     let (_db_dir, conn) = super::open_conn(&args.db_dir, super::OpenMode::ReadWrite)?;
     let db = std::sync::Arc::new(db::Database::new(clocks.clone(), conn, true).unwrap());
@@ -116,7 +116,7 @@ pub fn run(args: &Args) -> Result<(), Error> {
     } else {
         println!("s={}", encoded);
     }
-    Ok(())
+    Ok(0)
 }
 
 fn curl_cookie(cookie: &str, flags: i32, domain: &str) -> String {

server/src/cmds/mod.rs

@@ -59,12 +59,12 @@ fn open_dir(db_dir: &Path, mode: OpenMode) -> Result<dir::Fd, Error> {
                                    format!("db dir {} not found; try running moonfire-nvr init",
                                            db_dir.display())
                                } else {
-                                   format!("unable to open db dir {}: {}", db_dir.display(), &e)
+                                   format!("unable to open db dir {}", db_dir.display())
                                }))?;
     let ro = mode == OpenMode::ReadOnly;
     dir.lock(if ro { FlockArg::LockSharedNonblock } else { FlockArg::LockExclusiveNonblock })
-       .map_err(|e| e.context(format!("db dir {} already in use; can't get {} lock",
-                                      db_dir.display(), if ro { "shared" } else { "exclusive" })))?;
+       .map_err(|e| e.context(format!("unable to get {} lock on db dir {} ",
+                                      if ro { "shared" } else { "exclusive" }, db_dir.display())))?;
     Ok(dir)
 }
 

server/src/cmds/run.rs

@@ -175,7 +175,7 @@ struct Syncer {
 }
 
 #[tokio::main]
-pub async fn run(args: &Args) -> Result<(), Error> {
+pub async fn run(args: &Args) -> Result<i32, Error> {
     let clocks = clock::RealClocks {};
     let (_db_dir, conn) = super::open_conn(
         &args.db_dir,
@@ -323,5 +323,5 @@ pub async fn run(args: &Args) -> Result<(), Error> {
     info!("Waiting for HTTP requests to finish.");
     server_handle.await??;
     info!("Exiting.");
-    Ok(())
+    Ok(0)
 }

server/src/cmds/sql.rs

@@ -32,6 +32,7 @@
 
 use failure::Error;
 use std::ffi::OsString;
+use std::os::unix::process::CommandExt;
 use std::path::PathBuf;
 use std::process::Command;
 use super::OpenMode;
@@ -58,7 +59,7 @@ pub struct Args {
     arg: Vec<OsString>,
 }
 
-pub fn run(args: &Args) -> Result<(), Error> {
+pub fn run(args: &Args) -> Result<i32, Error> {
     let mode = if args.read_only { OpenMode::ReadOnly } else { OpenMode::ReadWrite };
     let _db_dir = super::open_dir(&args.db_dir, mode)?;
     let mut db = OsString::new();
@@ -68,6 +69,5 @@ pub fn run(args: &Args) -> Result<(), Error> {
     if args.read_only {
         db.push("?mode=ro");
     }
-    Command::new("sqlite3").arg(&db).args(&args.arg).status()?;
-    Ok(())
+    Err(Command::new("sqlite3").arg(&db).args(&args.arg).exec().into())
 }

server/src/cmds/ts.rs

@@ -43,10 +43,10 @@ pub struct Args {
     timestamps: Vec<String>,
 }
 
-pub fn run(args: &Args) -> Result<(), Error> {
+pub fn run(args: &Args) -> Result<i32, Error> {
     for timestamp in &args.timestamps {
         let t = db::recording::Time::parse(timestamp)?;
         println!("{} == {}", t, t.0);
     }
-    Ok(())
+    Ok(0)
 }

server/src/cmds/upgrade/mod.rs

@@ -59,12 +59,13 @@ pub struct Args {
     no_vacuum: bool,
 }
 
-pub fn run(args: &Args) -> Result<(), Error> {
+pub fn run(args: &Args) -> Result<i32, Error> {
     let (_db_dir, mut conn) = super::open_conn(&args.db_dir, super::OpenMode::ReadWrite)?;
 
     db::upgrade::run(&db::upgrade::Args {
         sample_file_dir: args.sample_file_dir.as_ref().map(std::path::PathBuf::as_path),
         preset_journal: &args.preset_journal,
         no_vacuum: args.no_vacuum,
-    }, &mut conn)
+    }, &mut conn)?;
+    Ok(0)
 }