Add search terms to Command and Signature (#4980)

* Add search terms to command

* Rename Signature desc to usage

To be named uniformly with extra_usage

* Throw in foldl search term for reduce

* Add missing usage to post

* Add search terms to signature

* Try to add capnp Signature serialization

crates/old/nu_plugin_chart/src/nu/bar.rs

@@ -129,7 +129,7 @@ fn display(model: &Model) -> Result<(), Box<dyn Error>> {
 impl Plugin for SubCommand {
     fn config(&mut self) -> Result<Signature, ShellError> {
         Ok(Signature::build("chart bar")
-            .desc("Bar charts")
+            .usage("Bar charts")
             .switch("acc", "accumulate values", Some('a'))
             .optional(
                 "columns",

crates/old/nu_plugin_chart/src/nu/line.rs

@@ -127,7 +127,7 @@ fn display(model: &Model) -> Result<(), Box<dyn Error>> {
 impl Plugin for SubCommand {
     fn config(&mut self) -> Result<Signature, ShellError> {
         Ok(Signature::build("chart line")
-            .desc("Line charts")
+            .usage("Line charts")
             .switch("acc", "accumulate values", Some('a'))
             .optional(
                 "columns",

crates/old/nu_plugin_from_bson/src/nu/mod.rs

@@ -10,7 +10,7 @@ use nu_source::Tag;
 impl Plugin for FromBson {
     fn config(&mut self) -> Result<Signature, ShellError> {
         Ok(Signature::build("from bson")
-            .desc("Convert from .bson binary into table")
+            .usage("Convert from .bson binary into table")
             .filter())
     }
 

crates/old/nu_plugin_from_mp4/src/nu/mod.rs

@@ -10,7 +10,7 @@ use nu_source::Tag;
 impl Plugin for FromMp4 {
     fn config(&mut self) -> Result<Signature, ShellError> {
         Ok(Signature::build("from mp4")
-            .desc("Get meta-data of mp4 file")
+            .usage("Get meta-data of mp4 file")
             .filter())
     }
 

crates/old/nu_plugin_from_sqlite/src/nu/mod.rs

@@ -33,7 +33,7 @@ impl Plugin for FromSqlite {
                 "Only convert specified tables",
                 Some('t'),
             )
-            .desc("Convert from sqlite binary into table")
+            .usage("Convert from sqlite binary into table")
             .filter())
     }
 

crates/old/nu_plugin_s3/src/nu/mod.rs

@@ -9,7 +9,7 @@ use crate::handler::s3_helper;
 impl Plugin for handler::Handler {
     fn config(&mut self) -> Result<Signature, ShellError> {
         Ok(Signature::build("s3")
-            .desc("Load S3 resource into a cell, convert to table if possible (avoid by appending '--raw' or '-R')")
+            .usage("Load S3 resource into a cell, convert to table if possible (avoid by appending '--raw' or '-R')")
             .required(
                 "RESOURCE",
                 SyntaxShape::String,

crates/old/nu_plugin_start/src/nu/mod.rs

@@ -7,7 +7,7 @@ use crate::start::Start;
 impl Plugin for Start {
     fn config(&mut self) -> Result<Signature, ShellError> {
         Ok(Signature::build("start")
-            .desc("Opens each file/directory/URL using the default application")
+            .usage("Opens each file/directory/URL using the default application")
             .rest(
                 "rest",
                 SyntaxShape::String,

crates/old/nu_plugin_to_bson/src/nu/mod.rs

@@ -10,7 +10,7 @@ use nu_source::Tag;
 impl Plugin for ToBson {
     fn config(&mut self) -> Result<Signature, ShellError> {
         Ok(Signature::build("to bson")
-            .desc("Convert table into .bson binary")
+            .usage("Convert table into .bson binary")
             .filter())
     }
 

crates/old/nu_plugin_to_sqlite/src/nu/mod.rs

@@ -10,7 +10,7 @@ use nu_source::Tag;
 impl Plugin for ToSqlite {
     fn config(&mut self) -> Result<Signature, ShellError> {
         Ok(Signature::build("to sqlite")
-            .desc("Convert table into sqlite binary")
+            .usage("Convert table into sqlite binary")
             .filter())
     }
 

crates/old/nu_plugin_tree/src/nu/mod.rs

@@ -7,7 +7,7 @@ use crate::TreeViewer;
 
 impl Plugin for TreeViewer {
     fn config(&mut self) -> Result<Signature, ShellError> {
-        Ok(Signature::build("tree").desc("View the contents of the pipeline as a tree."))
+        Ok(Signature::build("tree").usage("View the contents of the pipeline as a tree."))
     }
 
     fn sink(&mut self, _call_info: CallInfo, input: Vec<Value>) {