This reverts commit e3a49aa4.

Reason for revert:

TypeError: expected str, bytes or os.PathLike object, not NoneType

Original change's description:
> git-cl: Remove unused and duplicate functions.
> 
> Remove unused functions, and use scm.GIT where possible to reduce
> duplication.
> 
> Change-Id: I24f05e7b3ae04743e97b6665ee668f44d6acc294
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2116938
> Reviewed-by: Anthony Polito <apolito@google.com>
> Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>

TBR=ehmaldonado@chromium.org,apolito@google.com,infra-scoped@luci-project-accounts.iam.gserviceaccount.com,sokcevic@google.com

Change-Id: I334a6289eb2c1f3e20feddd428307542d2aa38a9
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2119411Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>