I loaded up Minecraft on 1.13 for the first time and it crashed.
I suspect it's to do with the fact that I use DropBox to merge the Saves folder between my Linux and Mac computers.
This relates to https://bugs.mojang.com/browse/MC-123021 but that has been resolved as Minecraft will run on Mac w/ DropBox in the latest snapshot.
I'm not sure why but Minecraft is fine for me on 18w32a but crashes in the actual 1.13 release

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---- Minecraft Crash Report -------- Minecraft Crash Report ----// I bet Cylons wouldn't have this problem.
Time: 09/08/18 14:16Description: Initializing game
java.lang.RuntimeException: java.nio.file.FileAlreadyExistsException: /Users/charles/Library/Application Support/minecraft/saves at cbp.<init>(SourceFile:38) at cbm.<init>(SourceFile:42) at cfi.am(SourceFile:463) at cfi.a(SourceFile:377) at net.minecraft.client.main.Main.main(SourceFile:144)Caused by: java.nio.file.FileAlreadyExistsException: /Users/charles/Library/Application Support/minecraft/saves at sun.nio.fs.UnixException.translateToIOException(UnixException.java:88) at sun.nio.fs.UnixException.rethrowAsIOException(UnixException.java:102) at sun.nio.fs.UnixException.rethrowAsIOException(UnixException.java:107) at sun.nio.fs.UnixFileSystemProvider.createDirectory(UnixFileSystemProvider.java:384) at java.nio.file.Files.createDirectory(Files.java:674) at java.nio.file.Files.createAndCheckIsDirectory(Files.java:781) at java.nio.file.Files.createDirectories(Files.java:727) at cbp.<init>(SourceFile:36) ... 4 more
A detailed walkthrough of the error, its code path and all known details is as follows:---------------------------------------------------------------------------------------
– Head --Thread: Client threadStacktrace: at cbp.<init>(SourceFile:38) at cbm.<init>(SourceFile:42) at cfi.am(SourceFile:463)
– Initialization --Details:Stacktrace: at cfi.a(SourceFile:377) at net.minecraft.client.main.Main.main(SourceFile:144)
– System Details --Details: Minecraft Version: 1.13 Operating System: Mac OS X (x86_64) version 10.13.6 Java Version: 1.8.0_74, Oracle Corporation Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation Memory: 818490888 bytes (780 MB) / 973078528 bytes (928 MB) up to 2147483648 bytes (2048 MB) JVM Flags: 8 total; -Xss1M -Xmx2G -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=32M Launched Version: 1.13 LWJGL: 3.1.6 build 14 OpenGL: Intel(R) HD Graphics 6000 GL version 2.1 INTEL-10.36.19, Intel Inc. GL Caps: Using GL 1.3 multitexturing.Using GL 1.3 texture combiners.Using framebuffer objects because ARB_framebuffer_object is supported and separate blending is supported.Shaders are available because OpenGL 2.1 is supported.VBOs are available because OpenGL 1.5 is supported.
Using VBOs: Yes Is Modded: Probably not. Jar signature remains and client brand is untouched. Type: Client (map_client.txt) Resource Packs:  Current Language: English (US) Profiler Position: N/A (disabled) CPU: 4x Intel(R) Core(TM) i5-5250U CPU @ 1.60GHz