regtest: Attempt to fix Client docs

The crate is not typical in that it expects at least one of the "verison
number" features to be enabled. This does not play nicely with the
docs.rs build. In an effort to make things at least uderstandable add do
a few things:

- inline the `Client` and `json` docs
- configure docs.rs build to enable 26_0
- Add a big fat note to hopefully alleviate the misleading
  "Available on crate feature 26_0 only."

regtest/Cargo.toml

@@ -65,7 +65,7 @@ anyhow = "1.0.66"
 
 
 [package.metadata.docs.rs]
-features = ["download", "doc"]
+features = ["download", "doc", "26_0"]
 rustdoc-args = ["--cfg", "docsrs"]
 
 [patch.crates-io.bitcoind-json-rpc-client]

regtest/src/client_versions.rs

@@ -1,4 +1,10 @@
 // All features uses 26_0
+/// The version specific client and json types.
+///
+/// **THIS IS AVAILABLE FOR ALL VERSION NUMBER FEATURES** (eg `25_0`, `24_2` etc). This crate is
+/// unusual in that it expects exactly one version number feature to be selected, docs.rs is not set
+/// up to handle such oddity.
+///
 #[cfg(feature = "26_0")]
 #[allow(unused_imports)] // Not all users need the json types.
 pub use bitcoind_json_rpc_client::{client_sync::v26::{Client, AddressType}, json::v26 as json};
@@ -67,7 +73,7 @@ pub use bitcoind_json_rpc_client::{client_sync::v18::{Client, AddressType}, json
 #[allow(unused_imports)] // Not all users need the json types.
 pub use bitcoind_json_rpc_client::{client_sync::v17::{Client, AddressType}, json::v17 as json};
 
-// To make --no-default-features work we have to enable some feature, use most recent version same as for default.
+// To make --no-default-features work we have to re-export a the types, use most recent version same as we do for all features.
 #[cfg(all(not(feature = "26_0"), not(feature = "25_2"), not(feature = "25_1"), not(feature = "25_0"), not(feature = "24_2"),not(feature = "24_1"), not(feature = "24_0_1"), not(feature = "23_2"), not(feature = "23_1"), not(feature = "23_0"), not(feature = "22_1"), not(feature = "22_0"), not(feature = "0_21_2"), not(feature = "0_20_2"), not(feature = "0_19_1"), not(feature = "0_18_1"), not(feature = "0_17_1")))]
 #[allow(unused_imports)] // Not all users need the json types.
 pub use bitcoind_json_rpc_client::{client_sync::v26::{Client, AddressType}, json::v26 as json};

regtest/src/lib.rs

@@ -21,6 +21,7 @@ use tempfile::TempDir;
 pub use {anyhow, tempfile, which};
 
 #[rustfmt::skip]                // Keep pubic re-exports separate.
+#[doc(inline)]
 pub use self::{
     client_versions::{json, Client, AddressType},
     versions::VERSION,