docs(ref): Note MSRV for features in the docs

I mostly focused on manifests and build scripts as those seemed the
highest priority.
I also went back only so far, assuming these would be the highest value
items.

Author: epage

src/doc/src/reference/build-scripts.md

@@ -77,13 +77,6 @@ Build scripts communicate with Cargo by printing to stdout. Cargo will
 interpret each line that starts with `cargo::` as an instruction that will
 influence compilation of the package. All other lines are ignored.
 
-> **Note:** The old invocation prefix `cargo:` (one colon only) is deprecated
-> and won't get any new features. To migrate, use two-colons prefix `cargo::`,
-> which was added in Rust 1.77. If you were using `cargo:KEY=VALUE` for
-> arbitrary links manifest key-value pairs, it is encouraged to switch to
-> `cargo::metadata=KEY=VALUE`. Stick to `cargo:` only if the support of Rust
-> version older than 1.77 is required.
-
 > The order of `cargo::` instructions printed by the build script *may*
 > affect the order of arguments that `cargo` passes to `rustc`. In turn, the
 > order of arguments passed to `rustc` may affect the order of arguments passed
@@ -140,6 +133,9 @@ one detailed below.
 * [`cargo::metadata=KEY=VALUE`](#the-links-manifest-key) --- Metadata, used by `links`
   scripts.
 
+> **MSRV:** 1.77 is required for `cargo::KEY=VALUE` syntax.
+> To support older versions, use the `cargo:KEY=VALUE` syntax.
+
 ### `cargo::rustc-link-arg=FLAG` {#rustc-link-arg}
 
 The `rustc-link-arg` instruction tells Cargo to pass the [`-C link-arg=FLAG`
@@ -264,8 +260,6 @@ the _reachable_ cfg expressions with the [`unexpected_cfgs`][unexpected-cfgs] li
 The syntax of `CHECK_CFG` mirrors the `rustc` [`--check-cfg` flag][option-check-cfg], see
 [Checking conditional configurations][checking-conditional-configurations] for more details.
 
-> Note: `cargo:rustc-check-cfg` (single-colon) can be used if your MSRV is below Rust 1.77
-
 The instruction can be used like this:
 
 ```rust,no_run
@@ -286,6 +280,8 @@ avoid typos, missing check-cfg, stale cfgs...
 See also the
 [conditional compilation][conditional-compilation-example] example.
 
+> **MSRV:** Respected as of 1.80
+
 [checking-conditional-configurations]: ../../rustc/check-cfg.html
 [option-check-cfg]: ../../rustc/command-line-arguments.md#option-check-cfg
 [conditional-compilation-example]: build-script-examples.md#conditional-compilation
@@ -430,6 +426,9 @@ used.
 Note that metadata is only passed to immediate dependents, not transitive
 dependents.
 
+> **MSRV:** 1.77 is required for `cargo::metadata=KEY=VALUE`.
+> To support older versions, use `cargo:KEY=VAUE` (unsupported directives are assumed to be metadata keys).
+
 [using-another-sys]: build-script-examples.md#using-another-sys-crate
 
 ## `*-sys` Packages

src/doc/src/reference/external-tools.md

@@ -54,6 +54,8 @@ details.
 If you are using Rust, the [cargo_metadata] crate can be used to parse these
 messages.
 
+> **MSRV:** 1.77 is required for `package_id` to be a Package ID Specification. Before that, it was opaque.
+
 [build command documentation]: ../commands/cargo-build.md
 [cargo_metadata]: https://crates.io/crates/cargo_metadata
 [Package ID Specifications]: ./pkgid-spec.md

src/doc/src/reference/manifest.md

@@ -111,6 +111,8 @@ breaking change.
 
 This field is optional and defaults to `0.0.0`.  The field is required for publishing packages.
 
+> **MSRV:** Before 1.75, this field was required
+
 [Resolver]: resolver.md
 [SemVer compatibility]: semver.md
 
@@ -189,6 +191,8 @@ To find the minimum `rust-version` compatible with your project, you can use thi
 
 When used on packages that get published, we recommend [verifying the `rust-version`](../guide/continuous-integration.md#verifying-rust-version).
 
+> **MSRV:** Respected as of 1.56
+
 ### The `description` field
 
 The description is a short blurb about the package. [crates.io] will display
@@ -589,6 +593,8 @@ Cargo only applies these to the current package and not to dependencies.
 As for dependents, Cargo suppresses lints from non-path dependencies with features like
 [`--cap-lints`](../../rustc/lints/levels.html#capping-lints).
 
+> **MSRV:** Respected as of 1.74
+
 ## The `[badges]` section
 
 The `[badges]` section is for specifying status badges that can be displayed

src/doc/src/reference/profiles.md

@@ -78,6 +78,8 @@ For more information on what each option does see `rustc`'s docs on [debuginfo].
 You may wish to also configure the [`split-debuginfo`](#split-debuginfo) option
 depending on your needs as well.
 
+> **MSRV:** 1.71 is required for `none`, `limited`, `full`, `line-directives-only`, and `line-tables-only`
+
 [`-C debuginfo` flag]: ../../rustc/codegen-options/index.html#debuginfo
 [debuginfo]: ../../rustc/codegen-options/index.html#debuginfo
 [profiling]: https://reviews.llvm.org/D46061

src/doc/src/reference/workspaces.md

@@ -191,6 +191,8 @@ description.workspace = true
 documentation.workspace = true
 ```
 
+> **MSRV:** Requires 1.74+
+
 ## The `dependencies` table
 
 The `workspace.dependencies` table is where you define dependencies to be
@@ -230,6 +232,8 @@ cc.workspace = true
 rand.workspace = true
 ```
 
+> **MSRV:** Requires 1.74+
+
 ## The `lints` table
 
 The `workspace.lints` table is where you define lint configuration to be inherited by members of a workspace.
@@ -257,6 +261,8 @@ version = "0.1.0"
 workspace = true
 ```
 
+> **MSRV:** Respected as of 1.74
+
 ## The `metadata` table
 
 The `workspace.metadata` table is ignored by Cargo and will not be warned