解决办法如下

aliangdeMacBook-Pro:~ aliang$ cd Desktop/
aliangdeMacBook-Pro:Desktop aliang$ git clone https://github.com/Cocoanetics/DTCoreText.git
Cloning into 'DTCoreText'...
remote: Enumerating objects: 14796, done.
remote: Total 14796 (delta 0), reused 0 (delta 0), pack-reused 14796
Receiving objects: 100% (14796/14796), 5.75 MiB | 428.00 KiB/s, done.
Resolving deltas: 100% (9996/9996), done.
aliangdeMacBook-Pro:Desktop aliang$ cd DTCoreText/
aliangdeMacBook-Pro:DTCoreText aliang$ cd Externals/
aliangdeMacBook-Pro:Externals aliang$ rm -rf DTFoundation/
aliangdeMacBook-Pro:Externals aliang$ git clone https://github.com/Cocoanetics/DTFoundation.git
Cloning into 'DTFoundation'...
remote: Enumerating objects: 6368, done.
remote: Total 6368 (delta 0), reused 0 (delta 0), pack-reused 6368
Receiving objects: 100% (6368/6368), 2.77 MiB | 398.00 KiB/s, done.
Resolving deltas: 100% (3793/3793), done.
aliangdeMacBook-Pro:Externals aliang$ cd ..
aliangdeMacBook-Pro:DTCoreText aliang$ open DTCoreText.xcodeproj/
aliangdeMacBook-Pro:DTCoreText aliang$