[docs] Remove out-of-date docs, improve header standardization. (#24456)

* Remove out-of-date docs, improve header standardization.

* PR scoping & comments

docs/examples/installing-and-using-packages.md

@@ -1,5 +1,7 @@
 ## Installing and Using Packages Example: SQLite
 
+_Note: this old example uses Classic Mode, but most developers will be happier with Manifest Mode. See [Manifest Mode: CMake Example](manifest-mode-cmake.md) for an example of converting to Manifest Mode._
+
   - [Step 1: Install](#install)
   - [Step 2: Use](#use)
     - [VS/MSBuild Project (User-wide integration)](#msbuild)

docs/examples/modify-baseline-to-pin-old-boost.md

@@ -2,7 +2,7 @@
 This document will teach you how to set versions of meta-packages like `boost` or `qt5`.
 
 **What is a meta-package?**
-In vcpkg we call meta-packages to ports that by themselves don't install anything but that instead forward installation to another port or ports. The reasons for these meta-packages to exist are plenty: to install different versions of a library depending on platform (like the old OpenSSL port did), to allow for multiple versions to exist in the vcpkg registry at the same time (OpenCV), or to conveniently install/uninstall a catalog of related packages (Boost and Qt).  
+In vcpkg we call meta-packages to ports that by themselves don't install anything but that instead forward installation to another port or ports. The reasons for these meta-packages to exist are plenty: to install different versions of a library depending on platform or to conveniently install/uninstall a catalog of related packages (Boost and Qt).
 
 In the case of Boost, it is unlikely that a user requires all of the 140+ Boost libraries in their project. For the sake of convenience, vcpkg splits Boost into multiple sub-packages broken down to individual libraries. By doing so, users can limit the subset of Boost libraries that they depend on.
 
@@ -74,12 +74,13 @@ The second method makes it easy to pin the entire Boost collection and end up wi
 ## Method 2: Modify baseline
 An easy way to set the version for the entirety of boost is to use the `"builtin-baseline"` property.
 
-As of right now, it is only possible to go back to Boost version `1.75.0` using a baseline. Since that was the contemporary Boost version when the versioning feature was merged. **But, it is possible to modify the baseline to whatever you like and use that instead.**
+As of right now, it is only possible to go back to Boost version `1.75.0` using a baseline, since that was the contemporary Boost version when the versioning feature was merged. **But, it is possible to modify the baseline to whatever you like and use that instead.**
 
 ### Step 1: Create a new branch
-As described in the versioning documentation. The value that goes in `"builtin-baseline"` is a Git commit in the vcpkg repository's history. Then it stands to reason, that if you want to customize the baseline you should be able to create a new commit with said custom baseline. 
+As described in the versioning documentation. The value that goes in `"builtin-baseline"` is a git commit in the microsoft/vcpkg repository's history. If you want to customize the baseline and have control over the vcpkg instance, you can create a new commit with said custom baseline.
 
 Let's start by creating a new branch to hold our modified baseline.
+
 In the directory containing your clone of the vcpkg Git repository run:
 
 ```

docs/examples/versioning.getting-started.md

@@ -6,8 +6,6 @@ Vcpkg lets you take control of which version of packages to install in your proj
 
 ## Using versions with manifests
 
-With the `versions` feature flag enabled you can start adding version constraints to your dependencies.
-
 Let's start with creating a simple CMake project that depends on `fmt` and `zlib`.
 
 Create a folder with the following files:
@@ -97,7 +95,7 @@ fmt[core]:x86-windows -> 7.1.3#1 -- D:\vcpkg\buildtrees\versioning\versions\fmt\
 zlib[core]:x86-windows -> 1.2.11#9 -- D:\vcpkg\buildtrees\versioning\versions\zlib\827111046e37c98153d9d82bb6fa4183b6d728e4
 ```
 
-Instead of using the portfiles in `ports/`, vcpkg is checking out the files for each version in `buildtrees/versioning/versions/`. The files in `ports/` are still used when running vcpkg in classic mode or when the `versions` feature flag is disabled. 
+Instead of using the portfiles in `ports/`, vcpkg is checking out the files for each version in `buildtrees/versioning/versions/`. The files in `ports/` are still used when running vcpkg in classic mode.
 
 _NOTE: Output from vcpkg while configuring CMake is only available when using CMake version `3.18` or newer. If you're using an older CMake you can check the `vcpkg-manifest-install.log` file in your build directory instead._
 
@@ -238,7 +236,7 @@ The last thing to discuss is how overlay ports interact with versioning resoluti
 
 Going into more detail, when you provide an overlay for a port, vcpkg will always use the overlay port without caring what version is contained in it. The reasons are two-fold: (1) it is consistent with the existing behavior of overlay ports of completely masking the existing port, and (2) overlay ports do not (and are not expected to) provide enough information to power vcpkg's versioning feature.
 
-If you want to have flexible port customization along with versioning features, you should consider making your own custom registry. See our [registries specification for more details](../specifications/registries.md).
+If you want to have flexible port customization along with versioning, you should consider making your own custom registry. See our [registries specification for more details](../specifications/registries.md).
 
 ## Further reading
 

docs/specifications/registries-2.md

@@ -2,6 +2,8 @@
 
 **Note: this is the feature as it was initially specified and does not necessarily reflect the current behavior.**
 
+**Up-to-date documentation is available at [Registries](../users/registries.md).**
+
 Originally, the design of registries was decided upon and written up in the [Registries RFC](registries.md).
 However, as we've gotten further into the design process of git registries and versioning,
 and discussed the interaction of versioning with registries,

docs/specifications/registries.md

@@ -2,6 +2,8 @@
 
 **Note: this is the feature as it was initially specified and does not necessarily reflect the current behavior.**
 
+**Up-to-date documentation is available at [Registries](../users/registries.md).**
+
 As it is now, vcpkg has over 1400 ports in the default registry (the `/ports` directory).
 For the majority of users, this repository of packages is enough. However, many enterprises
 need to more closely control their dependencies for one reason or another, and this document

docs/users/android.md

@@ -2,10 +2,7 @@
 
 **The latest version of this documentation is available on [GitHub](https://github.com/Microsoft/vcpkg/tree/master/docs/users/android.md).**
 
-Android is not officially supported, and there are no official android triplets at the moment.
-
-However, some packages can compile to Android, and the situation is improving: see the list of [PR related to Android](https://github.com/Microsoft/vcpkg/pulls?q=+android+).
-
+*Android is not tested as part of vcpkg repository's CI process, so regressions can occur as part of library updates. PRs improving support are welcome!*
 
 ## Android build requirements
 

docs/users/config-environment.md

@@ -14,9 +14,7 @@ This environment variable can be set to an existing directory to use for storing
 This environment variable can be set to a comma-separated list of off-by-default features in vcpkg. These features are
 subject to change without notice and should be considered highly unstable.
 
-Non-exhaustive list of off-by-default features:
-
-- `manifest`
+There are no off-by-default feature flags at this time.
 
 #### EDITOR
 

docs/users/mingw.md

@@ -2,7 +2,7 @@
 
 **The latest version of this documentation is available on [GitHub](https://github.com/Microsoft/vcpkg/tree/master/docs/users/mingw.md).**
 
-*MinGW is community-supported and not tested as part of vcpkg repository's CI process.*
+*MinGW is not tested as part of vcpkg repository's CI process, so regressions can occur as part of library updates. PRs improving support are welcome!*
 
 ## Table of Contents