Fixes the following security vulnerabilities:
* CVE-2019-1348:
The --export-marks option of git fast-import is exposed also via
the in-stream command feature export-marks=... and it allows
overwriting arbitrary paths.
* CVE-2019-1349:
When submodules are cloned recursively, under certain circumstances
Git could be fooled into using the same Git directory twice. We now
require the directory to be empty.
* CVE-2019-1350:
Incorrect quoting of command-line arguments allowed remote code
execution during a recursive clone in conjunction with SSH URLs.
* CVE-2019-1351:
While the only permitted drive letters for physical drives on
Windows are letters of the US-English alphabet, this restriction
does not apply to virtual drives assigned via subst <letter>:
<path>. Git mistook such paths for relative paths, allowing writing
outside of the worktree while cloning.
* CVE-2019-1352:
Git was unaware of NTFS Alternate Data Streams, allowing files
inside the .git/ directory to be overwritten during a clone.
* CVE-2019-1353:
When running Git in the Windows Subsystem for Linux (also known as
"WSL") while accessing a working directory on a regular Windows
drive, none of the NTFS protections were active.
* CVE-2019-1354:
Filenames on Linux/Unix can contain backslashes. On Windows,
backslashes are directory separators. Git did not use to refuse to
write out tracked files with such filenames.
* CVE-2019-1387:
Recursive clones are currently affected by a vulnerability that is
caused by too-lax validation of submodule names, allowing very
targeted attacks via remote code execution in recursive clones.
* CVE-2019-19604:
The git submodule update operation can lead to execution of arbitrary
shell commands defined in the .gitmodules file
https://gitlab.com/gitlab-com/gl-security/disclosures/blob/master/003_git_submodule/advisory.md
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>