This introduces the functionality of submodule update in
'git_submodule_do_update'. The existing 'git_submodule_update' function is
renamed to 'git_submodule_update_strategy'. The 'git_submodule_update'
function now refers to functionality similar to `git submodule update`,
while `git_submodule_update_strategy` is used to get the configured value
of submodule.<name>.update.
Path validation may be influenced by `core.protectHFS` and
`core.protectNTFS` configuration settings, thus treebuilders
can take a repository to influence their configuration.
HFS filesystems ignore some characters like U+200C. When these
characters are included in a path, they will be ignored for the
purposes of comparison with other paths. Thus, if you have a ".git"
folder, a folder of ".git<U+200C>" will also match. Protect our
".git" folder by ensuring that ".git<U+200C>" and friends do not match it.
Disallow:
1. paths with trailing dot
2. paths with trailing space
3. paths with trailing colon
4. paths that are 8.3 short names of .git folders ("GIT~1")
5. paths that are reserved path names (COM1, LPT1, etc).
6. paths with reserved DOS characters (colons, asterisks, etc)
These paths would (without \\?\ syntax) be elided to other paths - for
example, ".git." would be written as ".git". As a result, writing these
paths literally (using \\?\ syntax) makes them hard to operate with from
the shell, Windows Explorer or other tools. Disallow these.
When turning UTF-8 paths into UCS-2 paths for Windows, always use
the \\?\-prefixed paths. Because this bypasses the system's
path canonicalization, handle the canonicalization functions ourselves.
We must:
1. always use a backslash as a directory separator
2. only use a single backslash between directories
3. not rely on the system to translate "." and ".." in paths
4. remove trailing backslashes, except at the drive root (C:\)
We do not currently generate any messages when we're counting the
objects, as might be expected from a local upload-pack. Assert that we
do call the function when working.
Most of the network-facing facilities have been copied to the socket and
openssl streams. No code now uses these functions directly anymore, so
we can now remove them.
Having an ssh stream would require extra work for stream capabilities we
don't need anywhere else (oob auth and command execution) so for now
let's move away from the gitno connection to use socket_stream.
We can introduce an ssh stream interface if and as we need it.
