Sync with 2.19.3

* maint-2.19: (34 commits)
  Git 2.19.3
  Git 2.18.2
  Git 2.17.3
  Git 2.16.6
  test-drop-caches: use `has_dos_drive_prefix()`
  Git 2.15.4
  Git 2.14.6
  mingw: handle `subst`-ed "DOS drives"
  mingw: refuse to access paths with trailing spaces or periods
  mingw: refuse to access paths with illegal characters
  unpack-trees: let merged_entry() pass through do_add_entry()'s errors
  quote-stress-test: offer to test quoting arguments for MSYS2 sh
  t6130/t9350: prepare for stringent Win32 path validation
  quote-stress-test: allow skipping some trials
  quote-stress-test: accept arguments to test via the command-line
  tests: add a helper to stress test argument quoting
  mingw: fix quoting of arguments
  Disallow dubiously-nested submodule git directories
  protect_ntfs: turn on NTFS protection by default
  path: also guard `.gitmodules` against NTFS Alternate Data Streams
  ...

Documentation/RelNotes/2.14.6.txt

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+Git v2.14.6 Release Notes
+=========================
+
+This release addresses the security issues CVE-2019-1348,
+CVE-2019-1349, CVE-2019-1350, CVE-2019-1351, CVE-2019-1352,
+CVE-2019-1353, CVE-2019-1354, and CVE-2019-1387.
+
+Fixes since v2.14.5
+-------------------
+
+ * 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.
+
+Credit for finding these vulnerabilities goes to Microsoft Security
+Response Center, in particular to Nicolas Joly. The `fast-import`
+fixes were provided by Jeff King, the other fixes by Johannes
+Schindelin with help from Garima Singh.

Documentation/RelNotes/2.15.4.txt

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+Git v2.15.4 Release Notes
+=========================
+
+This release merges up the fixes that appear in v2.14.6 to address
+the security issues CVE-2019-1348, CVE-2019-1349, CVE-2019-1350,
+CVE-2019-1351, CVE-2019-1352, CVE-2019-1353, CVE-2019-1354, and
+CVE-2019-1387; see the release notes for that version for details.
+
+In conjunction with a vulnerability that was fixed in v2.20.2,
+`.gitmodules` is no longer allowed to contain entries of the form
+`submodule.<name>.update=!command`.

Documentation/RelNotes/2.16.6.txt

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+Git v2.16.6 Release Notes
+=========================
+
+This release merges up the fixes that appear in v2.14.6 and in
+v2.15.4 addressing the security issues CVE-2019-1348, CVE-2019-1349,
+CVE-2019-1350, CVE-2019-1351, CVE-2019-1352, CVE-2019-1353,
+CVE-2019-1354, and CVE-2019-1387; see the release notes for those
+versions for details.

Documentation/RelNotes/2.17.3.txt

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+Git v2.17.3 Release Notes
+=========================
+
+This release merges up the fixes that appear in v2.14.6 and in
+v2.15.4 addressing the security issues CVE-2019-1348, CVE-2019-1349,
+CVE-2019-1350, CVE-2019-1351, CVE-2019-1352, CVE-2019-1353,
+CVE-2019-1354, and CVE-2019-1387; see the release notes for those
+versions for details.
+
+In addition, `git fsck` was taught to identify `.gitmodules` entries
+of the form `submodule.<name>.update=!command`, which have been
+disallowed in v2.15.4.

Documentation/RelNotes/2.18.2.txt

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+Git v2.18.2 Release Notes
+=========================
+
+This release merges up the fixes that appear in v2.14.6, v2.15.4
+and in v2.17.3, addressing the security issues CVE-2019-1348,
+CVE-2019-1349, CVE-2019-1350, CVE-2019-1351, CVE-2019-1352,
+CVE-2019-1353, CVE-2019-1354, and CVE-2019-1387; see the release notes
+for those versions for details.

Documentation/RelNotes/2.19.3.txt

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+Git v2.19.3 Release Notes
+=========================
+
+This release merges up the fixes that appear in v2.14.6, v2.15.4
+and in v2.17.3, addressing the security issues CVE-2019-1348,
+CVE-2019-1349, CVE-2019-1350, CVE-2019-1351, CVE-2019-1352,
+CVE-2019-1353, CVE-2019-1354, and CVE-2019-1387; see the release notes
+for those versions for details.