Updated MacOS docs

Author: Chris Piker

README.md

@@ -36,10 +36,17 @@ prequisites are provided below \.\.\.
 $ sudo yum install expat-devel fftw-devel openssl-devel             # RedHat 7 and similar
 $ sudo apt install libexpat-dev libfftw3-dev libssl-dev zlib1g-dev  # Debian 9 and similar
 ```
-And on windows using [vcpkg](https://github.com/microsoft/vcpkg).
+and on windows using [vcpkg](https://github.com/microsoft/vcpkg)\.\.\.
 ```batchfile
 > vcpkg install openssl fftw3 zlib expat pthreads --triplet x64-windows-static
 ```
+or on mac using [brew](https://brew.sh)
+```bash
+$ brew install openssl
+$ brew install fftw
+```
+The expat library should already be present on MacOS once the compiler install
+command `xcode-select --install` has been run.
 
 ## Build and Install
 

doc/install_fedora.txt

@@ -61,10 +61,10 @@ the following commands.  Pressing Y as needed.
 ========================
 
    $ cd 
-   $ mkdir svn
-   $ cd svn
-   $ svn co https://saturn.physics.uiowa.edu/svn/das2/core/stable/libdas2_3
-   $ cd libdas2
+   $ mkdir git
+   $ cd git
+   $ git clone https://github.com/das-developers/das2C.git
+   $ cd das2C
 
 
 4. Set environment variables

doc/install_mac.txt

@@ -27,15 +27,15 @@ installer for which will expect mouse clicks to proceeds.
 
 After installing XCode check that you have the tools run:
 
-  $ svn -version
+  $ git -version
 
 and you should see a bit of diagnostic information about the subversion tool
-printed to the screen.  If instead you see the message:  "-bash: svn: command
+printed to the screen.  If instead you see the message:  "-bash: git: command
 not found", then svn is not installed.
 
 To check that you have a compiler run
 
-  $ gcc --version
+  $ clang --version
 
 and you should see a small bit of diagnostic information about the compiler, 
 if instead the output is "-bash: gcc: command not found" then gcc is not
@@ -57,8 +57,7 @@ It install homebrew (from https://brew.sh ):
 To test that it's installed run:
 
   $ brew --version
-  
-  
+
 3. Install prerequisite libraires
 =================================
 To install the header files and libraies needed to compile libdas2 run
@@ -72,10 +71,10 @@ the following commands:
 ========================
 
    $ cd 
-   $ mkdir svn
-   $ cd svn
-   $ svn co https://saturn.physics.uiowa.edu/svn/das2/core/stable/libdas2_3
-   $ cd libdas2
+   $ mkdir git
+   $ cd git
+   $ git clone https://github.com/das-developers/das2C.git
+   $ cd das2C
 
 4. Set environment variables
 ============================