错误描述：

$ git pull origin alpha

From https://github.com/shirley-wu/HeartTrace

 * branch            alpha      -> FETCH_HEAD

error: The following untracked working tree files would be overwritten by merge:

        .gradle/4.4/fileChanges/last-build.bin

        .gradle/4.4/fileHashes/fileHashes.bin

        .gradle/4.4/fileHashes/fileHashes.lock

        .gradle/4.4/fileHashes/resourceHashesCache.bin

        .gradle/4.4/taskHistory/taskHistory.bin

        .gradle/4.4/taskHistory/taskHistory.lock

        .gradle/buildOutputCleanup/buildOutputCleanup.lock

        .gradle/buildOutputCleanup/cache.properties

        .gradle/buildOutputCleanup/outputFiles.bin

        .idea/gradle.xml

        .idea/workspace.xml

        app/app.iml

        app/build/generated/res/pngs/debug/drawable-anydpi-v21/ic_launcher_background.xml

        app/build/generated/res/pngs/debug/drawable-hdpi/ic_launcher_background.png

        app/build/generated/res/pngs/debug/drawable-ldpi/ic_launcher_background.png

        app/build/generated/res/pngs/debug/drawable-mdpi/ic_launcher_background.png

        app/build/generated/res/pngs/debug/drawable-xhdpi/ic_launcher_background.png

        app/build/generated/res/pngs/debug/drawable-xxhdpi/ic_launcher_background.png

        app/build/generated/res/pngs/debug/drawable-xxxhdpi/ic_launcher_background.png

        app/build/generated/source/buildConfig/debug/com/example/dell/diary/BuildConfig.java

        app/build/generated/source/r/debug/android/arch/lifecycle/R.java

        app/build/generated/source/r/debug/android/support/compat/R.java

        app/build/generated/source/r/debug/android/support/constraint/R.java

        app/build/generated/source/r/debug/android/support/coreui/R.java

        app/build/generated/source/r/debug/android/support/coreutils/R.java

        app/build/generated/source/r/debug/android/support/design/R.java

        app/build/generated/source/r/debug/android/support/fragment/R.java

        app/build/generated/source/r/debug/android/support/graphics/drawable/R.java

        app/build/generated/source/r/debug/android/support/graphics/drawable/animated/R.java

        app/build/generated/source/r/debug/android/support/mediacompat/R.java

        app/build/generated/source/r/debug/android/support/transition/R.java

        app/build/generated/source/r/debug/android/support/v4/R.java

        app/build/generated/source/r/debug/android/support/v7/appcompat/R.java

        app/build/generated/source/r/debug/android/support/v7/cardview/R.java

        app/build/generated/source/r/debug/android/support/v7/recyclerview/R.java

        app/build/generated/source/r/debug/com/bigkoo/pickerview/R.java

        app/build/generated/source/r/debug/com/borax12/materialdaterangepicker/R.java

        app/build/generated/source/r/debug/com/contrarywind/view/R.java

        app/build/generated/source/r/debug/com/example/dell/diary/R.java

        app/build/generated/source/r/debug/com/google/android/gms/R.java

        app/build/generated/source/r/debug/com/google/android/gms/appindexing/R.java

        app/build/generated/source/r/debug/com/google/android/gms/base/R.java

        app/build/generated/source/r/debug/com/google/android/gms/tasks/R.java

        app/build/generated/source/r/debug/com/google/firebase/R.java

        app/build/generated/source/r/debug/com/prolificinteractive/materialcalendarview/R.java

        app/build/generated/source/r/debug/de/hdodenhof/circleimageview/R.java

        app/build/generated/source/r/debug/net/sqlcipher/R.java

        app/build/generated/source/r/debug/org/adw/library/widgets/discreteseekbar/R.java

        app/build/intermediates/blame/res/debug/multi-v2/values-af.json

        app/build/intermediates/blame/res/debug/multi-v2/values-am.json

        app/build/intermediates/blame/res/debug/multi-v2/values-ar.json

        app/build/intermediates/blame/res/debug/multi-v2/values-az.json

        app/build/intermediates/blame/res/debug/multi-v2/values-b+sr+Latn.json

        app/build/intermediates/blame/res/debug/multi-v2/values-be.json

        app/build/intermediates/blame/res/debug/multi-v2/values-bg.json

        app/build/intermediates/blame/res/debug/multi-v2/values-bn.json

        app/build/intermediates/blame/res/debug/multi-v2/values-bs.json

        app/build/intermediates/blame/res/debug/multi-v2/values-ca.json

        app/build/intermediates/blame/res/debug/multi-v2/values-cs.json

        app/build/intermediates/blame/res/debug/multi-v2/values-da.json

        app/build/intermediates/blame/res/debug/multi-v2/values-de.json

        app/build/intermediates/blame/res/debug/multi-v2/values-el.json

        app/build/intermediates/blame/res/debug/mul

Aborting   解决方法： git clean  -d  -fx git pull 手动merge git add . git commit -m "description"