Fix some html-proofer warnings

Author: ben

book/07-git-tools/sections/credentials.asc

@@ -20,8 +20,8 @@ Git has a few options provided in the box:
 * If you're using a Mac, Git comes with an "`osxkeychain`" mode, which caches credentials in the secure keychain that's attached to your system account.
   This method stores the credentials on disk, and they never expire, but they're encrypted with the same system that stores HTTPS certificates and Safari auto-fills.
 * If you're using Windows, you can enable the *Git Credential Manager* feature when installing https://gitforwindows.org/[Git for Windows] or separately install https://github.com/GitCredentialManager/git-credential-manager/releases/latest[the latest GCM] as a standalone service.
-  This is similar to the "`osxkeychain`" helper described above, but uses the Windows Credential Store to control sensitive information.  
-  It can also serve credentials to WSL1 or WSL2. See https://github.com/GitCredentialManager/git-credential-manager#windows[GCM Install Instructions] for more information.
+  This is similar to the "`osxkeychain`" helper described above, but uses the Windows Credential Store to control sensitive information.
+  It can also serve credentials to WSL1 or WSL2. See https://github.com/GitCredentialManager/git-credential-manager#readme[GCM Install Instructions] for more information.
 
 You can choose one of these methods by setting a Git configuration value:
 

book/09-git-and-other-scms/sections/client-p4.asc

@@ -15,12 +15,12 @@ The second is git-p4, a client-side bridge that lets you use Git as a Perforce c
 ===== Git Fusion
 
 (((Perforce, Git Fusion)))
-Perforce provides a product called Git Fusion (available at http://www.perforce.com/git-fusion[^]), which synchronizes a Perforce server with Git repositories on the server side.
+Perforce provides a product called Git Fusion (available at https://www.perforce.com/git-fusion[^]), which synchronizes a Perforce server with Git repositories on the server side.
 
 ====== Setting Up
 
 For our examples, we'll be using the easiest installation method for Git Fusion, which is downloading a virtual machine that runs the Perforce daemon and Git Fusion.
-You can get the virtual machine image from http://www.perforce.com/downloads/Perforce/20-User[^], and once it's finished downloading, import it into your favorite virtualization software (we'll use VirtualBox).
+You can get the virtual machine image from https://www.perforce.com/downloads/Perforce/20-User[^], and once it's finished downloading, import it into your favorite virtualization software (we'll use VirtualBox).
 
 Upon first starting the machine, it asks you to customize the password for three Linux users (`root`, `perforce`, and `git`), and provide an instance name, which can be used to distinguish this installation from others on the same network.
 When that has all completed, you'll see this:

book/A-git-in-other-environments/sections/zsh.asc

@@ -40,7 +40,7 @@ It looks a bit like this:
 .Customized `zsh` prompt
 image::images/zsh-prompt.png[Customized `zsh` prompt]
 
-For more information on `vcs_info`, check out its documentation in the `zshcontrib(1)` manual page, or online at http://zsh.sourceforge.net/Doc/Release/User-Contributions.html#Version-Control-Information[^].
+For more information on `vcs_info`, check out its documentation in the `zshcontrib(1)` manual page, or online at https://zsh.sourceforge.net/Doc/Release/User-Contributions.html#Version-Control-Information[^].
 
 Instead of `vcs_info`, you might prefer the prompt customization script that ships with Git, called `git-prompt.sh`; see https://github.com/git/git/blob/master/contrib/completion/git-prompt.sh[^] for details.
 `git-prompt.sh` is compatible with both Bash and Zsh.