After upgrading clang_format to version 3.8 I noticed that each time it formats a source file it leaves a .TMP file around. For example:
Changes not staged for commit: (use "git add <file>..." to update what will be committed) (use "git checkout -- <file>..." to discard changes in working directory modified: src/mongo/db/commands.cpp modified: src/mongo/db/commands.h Untracked files: (use "git add <file>..." to include in what will be committed) src/mongo/db/commands.cpp~RF3ac591c5.TMP src/mongo/db/commands.cpp~RF3aca5030.TMP src/mongo/db/commands.h~RF3ac591c5.TMP
Having these files around makes it difficult to run git add src/., because they will get added to the source tree as well.