Replace Mac with macOS when referring to the operating system

Apple's operating system for Macintosh computers is called macOS
(previously Mac OS). Referring to it with "on Mac" is not that common.
Alternatively, "on a Mac" can be used.

Author: easybe

book/01-introduction/sections/command-line.asc

@@ -7,5 +7,5 @@ For one, the command line is the only place you can run _all_ Git commands -- mo
 If you know how to run the command-line version, you can probably also figure out how to run the GUI version, while the opposite is not necessarily true.
 Also, while your choice of graphical client is a matter of personal taste, _all_ users will have the command-line tools installed and available.
 
-So we will expect you to know how to open Terminal in Mac or Command Prompt or PowerShell in Windows.
+So we will expect you to know how to open Terminal in macOS or Command Prompt or PowerShell in Windows.
 If you don't know what we're talking about here, you may need to stop and research that quickly so that you can follow the rest of the examples and descriptions in this book.

book/01-introduction/sections/installing.asc

@@ -31,7 +31,7 @@ $ sudo apt install git-all
 
 For more options, there are instructions for installing on several different Unix distributions on the Git website, at http://git-scm.com/download/linux[].
 
-==== Installing on Mac
+==== Installing on macOS
 
 (((Mac, installing)))
 There are several ways to install Git on a Mac.

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

@@ -69,7 +69,7 @@ Each of them is tailored for a specific purpose (viewing history and creating co
 ==== GitHub for Mac and Windows
 
 (((GitHub for Mac)))(((GitHub for Windows)))
-GitHub has created two workflow-oriented Git clients: one for Windows, and one for Mac.
+GitHub has created two workflow-oriented Git clients: one for Windows, and one for macOS.
 These clients are a good example of workflow-oriented tools – rather than expose _all_ of Git's functionality, they instead focus on a curated set of commonly-used features that work well together.
 They look like this:
 
@@ -84,7 +84,7 @@ We won't be doing a detailed rundown of these tools (they have their own documen
 
 * On the left is the list of repositories the client is tracking; you can add a repository (either by cloning or attaching locally) by clicking the ``+'' icon at the top of this area.
 * In the center is a commit-input area, which lets you input a commit message, and select which files should be included.
-  (On Windows, the commit history is displayed directly below this; on Mac, it's on a separate tab.)
+  (On Windows, the commit history is displayed directly below this; on macOS, it's on a separate tab.)
 * On the right is a diff view, which shows what's changed in your working directory, or which changes were included in the selected commit.
 * The last thing to notice is the ``Sync'' button at the top-right, which is the primary way you interact over the network.
 
@@ -114,10 +114,10 @@ The intended workflow for this tool is sometimes called the ``GitHub Flow.''
 We cover this in more detail in <<ch06-github#ch06-github_flow>>, but the general gist is that (a) you'll be committing to a branch, and (b) you'll be syncing up with a remote repository fairly regularly.
 
 Branch management is one of the areas where the two tools diverge.
-On Mac, there's a button at the top of the window for creating a new branch:
+On macOS, there's a button at the top of the window for creating a new branch:
 
-.``Create Branch'' button on Mac.
-image::images/branch_widget_mac.png[``Create Branch'' button on Mac.]
+.``Create Branch'' button on macOS.
+image::images/branch_widget_mac.png[``Create Branch'' button on macOS.]
 
 On Windows, this is done by typing the new branch's name in the branch-switching widget: