Update README.md (#4351)

README.md

@@ -21,7 +21,7 @@ For historical reasons this repository is called "visualfsharp" and currently al
 |**master**  |[![Build Status](https://ci2.dot.net/buildStatus/icon?job=Microsoft_visualfsharp/master/release_ubuntu14.04)](https://ci2.dot.net/job/Microsoft_visualfsharp/job/master/job/release_ubuntu14.04/)|[![Build Status](https://ci2.dot.net/buildStatus/icon?job=Microsoft_visualfsharp/master/debug_windows_nt)](https://ci2.dot.net/job/Microsoft_visualfsharp/job/master/job/debug_windows_nt/)|[![Build Status](https://ci2.dot.net/buildStatus/icon?job=Microsoft_visualfsharp/master/release_ci_part1_windows_nt)](https://ci2.dot.net/job/Microsoft_visualfsharp/job/master/job/release_ci_part1_windows_nt/)|[![Build Status](https://ci2.dot.net/buildStatus/icon?job=Microsoft_visualfsharp/master/release_ci_part2_windows_nt)](https://ci2.dot.net/job/Microsoft_visualfsharp/job/master/job/release_ci_part2_windows_nt/)|[![Build Status](https://ci2.dot.net/buildStatus/icon?job=Microsoft_visualfsharp/master/release_ci_part3_windows_nt)](https://ci2.dot.net/job/Microsoft_visualfsharp/job/master/job/release_ci_part3_windows_nt/)|
 |**dev15.5**  |[![Build Status](https://ci2.dot.net/buildStatus/icon?job=Microsoft_visualfsharp/dev15.5/release_ubuntu14.04)](https://ci2.dot.net/job/Microsoft_visualfsharp/job/dev15.5/job/release_ubuntu14.04/)|[![Build Status](https://ci2.dot.net/buildStatus/icon?job=Microsoft_visualfsharp/dev15.5/debug_windows_nt)](https://ci2.dot.net/job/Microsoft_visualfsharp/job/dev15.5/job/debug_windows_nt/)|[![Build Status](https://ci2.dot.net/buildStatus/icon?job=Microsoft_visualfsharp/dev15.5/release_ci_part1_windows_nt)](https://ci2.dot.net/job/Microsoft_visualfsharp/job/dev15.5/job/release_ci_part1_windows_nt/)|[![Build Status](https://ci2.dot.net/buildStatus/icon?job=Microsoft_visualfsharp/dev15.5/release_ci_part2_windows_nt)](https://ci2.dot.net/job/Microsoft_visualfsharp/job/dev15.5/job/release_ci_part2_windows_nt/)|[![Build Status](https://ci2.dot.net/buildStatus/icon?job=Microsoft_visualfsharp/dev15.5/release_ci_part3_windows_nt)](https://ci2.dot.net/job/Microsoft_visualfsharp/job/dev15.5/job/release_ci_part3_windows_nt/)|
 |**dev15.6**  |[![Build Status](https://ci2.dot.net/buildStatus/icon?job=Microsoft_visualfsharp/dev15.6/release_ubuntu14.04)](https://ci2.dot.net/job/Microsoft_visualfsharp/job/dev15.6/job/release_ubuntu14.04/)|[![Build Status](https://ci2.dot.net/buildStatus/icon?job=Microsoft_visualfsharp/dev15.6/debug_windows_nt)](https://ci2.dot.net/job/Microsoft_visualfsharp/job/dev15.6/job/debug_windows_nt/)|[![Build Status](https://ci2.dot.net/buildStatus/icon?job=Microsoft_visualfsharp/dev15.6/release_ci_part1_windows_nt)](https://ci2.dot.net/job/Microsoft_visualfsharp/job/dev15.6/job/release_ci_part1_windows_nt/)|[![Build Status](https://ci2.dot.net/buildStatus/icon?job=Microsoft_visualfsharp/dev15.6/release_ci_part2_windows_nt)](https://ci2.dot.net/job/Microsoft_visualfsharp/job/dev15.6/job/release_ci_part2_windows_nt/)|[![Build Status](https://ci2.dot.net/buildStatus/icon?job=Microsoft_visualfsharp/dev15.6/release_ci_part3_windows_nt)](https://ci2.dot.net/job/Microsoft_visualfsharp/job/dev15.6/job/release_ci_part3_windows_nt/)|
-
+|**dev15.7**  |[![Build Status](https://ci2.dot.net/buildStatus/icon?job=Microsoft_visualfsharp/dev15.7/release_ubuntu14.04)](https://ci2.dot.net/job/Microsoft_visualfsharp/job/dev15.7/job/release_ubuntu14.04/)|[![Build Status](https://ci2.dot.net/buildStatus/icon?job=Microsoft_visualfsharp/dev15.7/debug_windows_nt)](https://ci2.dot.net/job/Microsoft_visualfsharp/job/dev15.7/job/debug_windows_nt/)|[![Build Status](https://ci2.dot.net/buildStatus/icon?job=Microsoft_visualfsharp/dev15.7/release_ci_part1_windows_nt)](https://ci2.dot.net/job/Microsoft_visualfsharp/job/dev15.7/job/release_ci_part1_windows_nt/)|[![Build Status](https://ci2.dot.net/buildStatus/icon?job=Microsoft_visualfsharp/dev15.7/release_ci_part2_windows_nt)](https://ci2.dot.net/job/Microsoft_visualfsharp/job/dev15.7/job/release_ci_part2_windows_nt/)|[![Build Status](https://ci2.dot.net/buildStatus/icon?job=Microsoft_visualfsharp/dev15.7/release_ci_part3_windows_nt)](https://ci2.dot.net/job/Microsoft_visualfsharp/job/dev15.7/job/release_ci_part3_windows_nt/)|
 
 ## Help improve the Quality of the Tools by Using the Nightly Releases of Visual F# Tools
 To setup Visual Studio to use the latest nightly releases of the Visual F# Tools:
@@ -36,6 +36,25 @@ See [CONTRIBUTING.md](CONTRIBUTING.md) for general guidelines on the contributio
 
 To contribute to the F# ecosystem more generally see the F# Software Foundation's [Community Projects](http://fsharp.org/community/projects/) pages.
 
+## Branches
+
+These are the branches in use:
+
+* `master` = Latest branch for OSS developers and nightly users.  
+  - Most contributions go here.
+  - Able to be built, installed and used in the latest public Visual Studio release.
+  - May contain updated F# features and logic.
+  - Used to build nightly VSIX (see above).
+  - Gets integrated into https://github.com/fsharp/fsharp to form the basis of Mono releases
+  - Gets integrated into https://github.com/fsharp/FSharp.Compiler.Service to form the basis of FSharp.Compiler.Service releases
+
+* `dev15.x`
+  - Latest release branch for the particular point release of Visual Studio.
+  - Incorporates features and fixes from master up to a particular branch point, then selective cherry-picks.
+  - May contain new features that depend on new things or fixes in th corresponding Visual Studio release.
+  - Gets ingegrated back into master once the corresponding Visual Studio release is made.
+  - Used to build Visual F# Tool updates
+
 
 ### Technical Documentation