Preserve peers.toml formatting on writes

Author: myobie

CHANGELOG.md

@@ -8,6 +8,10 @@ EXPERIMENTAL, so on-disk formats and the CLI may change without notice.
 
 ### Fixed
 
+- **Fabric commands no longer replace the formatting in `peers.toml`.** Add,
+  remove, policy, and Git remote changes update only the affected entries.
+  User comments, spacing, order, and an edited or removed file header remain.
+
 - **A failed tunnel no longer reuses one bad shared connection forever.**
   Fabric counts post-admission attach failures on the exact current connection.
   Three consecutive failures replace it. Only sustained application progress

Cargo.lock

@@ -34,6 +34,7 @@ serde_json = "1"
 tokio = { version = "1", features = ["full"] }
 tokio-util = "0.7"
 toml = "0.9"
+toml_edit = "0.25"
 tracing = "0.1"
 tracing-appender = "0.2"
 tracing-subscriber = { version = "0.3", features = ["env-filter"] }

Cargo.toml

@@ -1214,6 +1214,10 @@ human-editable and can be provisioned before Fabric ever runs. The top-level
 `allow_shell` and `allow_exec` fields control the services this machine offers.
 Each field defaults to false. Each `[[peers]]` entry accepts:
 
+Fabric commands update this file in place. They preserve comments, spacing,
+entry order, and changes to the generated header. Fabric writes the default
+header only when it creates a new file.
+
 - `id` (required): the peer's 64-character hexadecimal iroh NodeID.
 - `name` (optional): a non-empty, unique local alias for commands such as
   `fabric ping workstation`.