Commit Graph

101935 Commits

Author SHA1 Message Date
Jeff Hostetler
13ba7c686f fscache: make fscache_enabled() public
Make fscache_enabled() function public rather than static.
Remove unneeded fscache_is_enabled() function.
Change is_fscache_enabled() macro to call fscache_enabled().

is_fscache_enabled() now takes a pathname so that the answer
is more precise and mean "is fscache enabled for this pathname",
since fscache only stores repo-relative paths and not absolute
paths, we can avoid attempting lookups for absolute paths.

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
2019-08-09 21:45:43 +02:00
Jeff Hostetler
1596e89a77 dir.c: make add_excludes aware of fscache during status
Teach read_directory_recursive() and add_excludes() to
be aware of optional fscache and avoid trying to open()
and fstat() non-existant ".gitignore" files in every
directory in the worktree.

The current code in add_excludes() calls open() and then
fstat() for a ".gitignore" file in each directory present
in the worktree.  Change that when fscache is enabled to
call lstat() first and if present, call open().

This seems backwards because both lstat needs to do more
work than fstat.  But when fscache is enabled, fscache will
already know if the .gitignore file exists and can completely
avoid the IO calls.  This works because of the lstat diversion
to mingw_lstat when fscache is enabled.

This reduced status times on a 350K file enlistment of the
Windows repo on a NVMe SSD by 0.25 seconds.

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
2019-08-09 21:45:43 +02:00
Jeff Hostetler
3da788882b add: use preload-index and fscache for performance
Teach "add" to use preload-index and fscache features
to improve performance on very large repositories.

During an "add", a call is made to run_diff_files()
which calls check_remove() for each index-entry.  This
calls lstat().  On Windows, the fscache code intercepts
the lstat() calls and builds a private cache using the
FindFirst/FindNext routines, which are much faster.

Somewhat independent of this, is the preload-index code
which distributes some of the start-up costs across
multiple threads.

We need to keep the call to read_cache() before parsing the
pathspecs (and hence cannot use the pathspecs to limit any preload)
because parse_pathspec() is using the index to determine whether a
pathspec is, in fact, in a submodule. If we would not read the index
first, parse_pathspec() would not error out on a path that is inside
a submodule, and t7400-submodule-basic.sh would fail with

	not ok 47 - do not add files from a submodule

We still want the nice preload performance boost, though, so we simply
call read_cache_preload(&pathspecs) after parsing the pathspecs.

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:43 +02:00
Johannes Schindelin
1e85b91b66 fscache: add a test for the dir-not-found optimization
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:42 +02:00
Jeff Hostetler
3c0f191242 fscache: remember not-found directories
Teach FSCACHE to remember "not found" directories.

This is a performance optimization.

FSCACHE is a performance optimization available for Windows.  It
intercepts Posix-style lstat() calls into an in-memory directory
using FindFirst/FindNext.  It improves performance on Windows by
catching the first lstat() call in a directory, using FindFirst/
FindNext to read the list of files (and attribute data) for the
entire directory into the cache, and short-cut subsequent lstat()
calls in the same directory.  This gives a major performance
boost on Windows.

However, it does not remember "not found" directories.  When STATUS
runs and there are missing directories, the lstat() interception
fails to find the parent directory and simply return ENOENT for the
file -- it does not remember that the FindFirst on the directory
failed. Thus subsequent lstat() calls in the same directory, each
re-attempt the FindFirst.  This completely defeats any performance
gains.

This can be seen by doing a sparse-checkout on a large repo and
then doing a read-tree to reset the skip-worktree bits and then
running status.

This change reduced status times for my very large repo by 60%.

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:42 +02:00
Jeff Hostetler
bd9daabb92 fscache: add key for GIT_TRACE_FSCACHE
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:42 +02:00
Karsten Blees
ca36daf202 fscache: load directories only once
If multiple threads access a directory that is not yet in the cache, the
directory will be loaded by each thread. Only one of the results is added
to the cache, all others are leaked. This wastes performance and memory.

On cache miss, add a future object to the cache to indicate that the
directory is currently being loaded. Subsequent threads register themselves
with the future object and wait. When the first thread has loaded the
directory, it replaces the future object with the result and notifies
waiting threads.

Signed-off-by: Karsten Blees <blees@dcon.de>
2019-08-09 21:45:42 +02:00
Karsten Blees
ff61a285c5 Win32: add a cache below mingw's lstat and dirent implementations
Checking the work tree status is quite slow on Windows, due to slow lstat
emulation (git calls lstat once for each file in the index). Windows
operating system APIs seem to be much better at scanning the status
of entire directories than checking single files.

Add an lstat implementation that uses a cache for lstat data. Cache misses
read the entire parent directory and add it to the cache. Subsequent lstat
calls for the same directory are served directly from the cache.

Also implement opendir / readdir / closedir so that they create and use
directory listings in the cache.

The cache doesn't track file system changes and doesn't plug into any
modifying file APIs, so it has to be explicitly enabled for git functions
that don't modify the working copy.

Note: in an earlier version of this patch, the cache was always active and
tracked file system changes via ReadDirectoryChangesW. However, this was
much more complex and had negative impact on the performance of modifying
git commands such as 'git checkout'.

Signed-off-by: Karsten Blees <blees@dcon.de>
2019-08-09 21:45:42 +02:00
Karsten Blees
b072bd25eb add infrastructure for read-only file system level caches
Add a macro to mark code sections that only read from the file system,
along with a config option and documentation.

This facilitates implementation of relatively simple file system level
caches without the need to synchronize with the file system.

Enable read-only sections for 'git status' and preload_index.

Signed-off-by: Karsten Blees <blees@dcon.de>
2019-08-09 21:45:42 +02:00
Karsten Blees
d7db47216a Win32: make the lstat implementation pluggable
Emulating the POSIX lstat API on Windows via GetFileAttributes[Ex] is quite
slow. Windows operating system APIs seem to be much better at scanning the
status of entire directories than checking single files. A caching
implementation may improve performance by bulk-reading entire directories
or reusing data obtained via opendir / readdir.

Make the lstat implementation pluggable so that it can be switched at
runtime, e.g. based on a config option.

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:42 +02:00
Karsten Blees
453a83c30a Win32: Make the dirent implementation pluggable
Emulating the POSIX dirent API on Windows via FindFirstFile/FindNextFile is
pretty staightforward, however, most of the information provided in the
WIN32_FIND_DATA structure is thrown away in the process. A more
sophisticated implementation may cache this data, e.g. for later reuse in
calls to lstat.

Make the dirent implementation pluggable so that it can be switched at
runtime, e.g. based on a config option.

Define a base DIR structure with pointers to readdir/closedir that match
the opendir implementation (i.e. similar to vtable pointers in OOP).
Define readdir/closedir so that they call the function pointers in the DIR
structure. This allows to choose the opendir implementation on a
call-by-call basis.

Move the fixed sized dirent.d_name buffer to the dirent-specific DIR
structure, as d_name may be implementation specific (e.g. a caching
implementation may just set d_name to point into the cache instead of
copying the entire file name string).

Signed-off-by: Karsten Blees <blees@dcon.de>
2019-08-09 21:45:42 +02:00
Karsten Blees
663ea9512c Win32: dirent.c: Move opendir down
Move opendir down in preparation for the next patch.

Signed-off-by: Karsten Blees <blees@dcon.de>
2019-08-09 21:45:41 +02:00
Karsten Blees
74914501ec Win32: make FILETIME conversion functions public
We will use them in the upcoming "FSCache" patches (to accelerate
sequential lstat() calls).

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:41 +02:00
Johannes Schindelin
ea1c5712c5 Merge branch 'work-around-isilon'
It would appear that least the Isilon network filesystem (and possibly
other network filesystems, too), report non-standard error values when
trying to access a non-existing directory.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:37 +02:00
Johannes Schindelin
207018b155 Merge branch 'dont-clean-junctions'
This topic branch teaches `git clean` to respect NTFS junctions and Unix
bind mounts: it will now stop at those boundaries.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:36 +02:00
Johannes Schindelin
631c9f7f14 Merge branch 'msys2-python'
In MSYS2, we have two Python interpreters at our disposal, so we can
include the Python stuff in the build.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:36 +02:00
Johannes Schindelin
e04d076c4b Merge branch 'msys2-strace'
Debugging support on MSYS2.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:35 +02:00
Johannes Schindelin
e3bcee2772 Merge branch 'robustify-is-hidden-tests'
In Git for Windows, there is an option to mark the .git directory as
hidden. Our test cases verify this by using the system utility
`attrib.exe`.

This file name is unfortunately quite generic, and overlaps with a
Unix-y utility that might be hiding the system one in the `PATH`.

Let's specify explicitly which `attrib` to use.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:35 +02:00
Johannes Schindelin
ef9b3ec1cf Merge branch 'fflush-in-git-clean'
After writing to `stdout` and before reading from `stdin`, it is a good
idea to flush the former.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:35 +02:00
Johannes Schindelin
a9ccc8c32d Merge branch 'avoid-pipes-in-svn-tests'
It is a good idea in general to avoid pipes in test cases, as it makes
things more debuggable to have files to inspect (instead of ephemereal
piped data that is long gone).

This also seemed to work around a problem where MSYS2' Perl would
segfault which may, or may not, still be present today.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:34 +02:00
Johannes Schindelin
6d6ffd7c6f Merge pull request #2170 from dscho/gitk-long-cmdline
Fix gitk (long cmdline)
2019-08-09 21:45:34 +02:00
Johannes Schindelin
2072e1eabe Merge branch 'fsync-object-files-always'
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:34 +02:00
Johannes Schindelin
c3bcda4542 Merge branch 'program-data-config'
This branch introduces support for reading the "Windows-wide" Git
configuration from `%PROGRAMDATA%\Git\config`. As these settings are
intended to be shared between *all* Git-related software, that config
file takes an even lower precedence than `$(prefix)/etc/gitconfig`.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:33 +02:00
Johannes Schindelin
ac8665dc6f Merge pull request #2148 from dscho/azure-pipelines-msvc
Let the MSVC build also be tested in the Azure Pipeline
2019-08-09 21:45:33 +02:00
Johannes Schindelin
d3a7280a2e Merge remote-tracking branch 'dscho/add-p' into add-p-g4w
Let's test this for a while.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:33 +02:00
Johannes Schindelin
5d7237335e Merge branch 'dont-spawn-gzip-in-archive'
This topic branch avoids spawning `gzip` when asking `git archive` to
create `.tar.gz` files.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:32 +02:00
Johannes Schindelin
db61781bca Merge pull request #1915 from dscho/open-in-gdb
Add a helper function to start GDB that was already attached to the current process
2019-08-09 21:45:32 +02:00
Johannes Schindelin
ede7a3898e Merge branch 'mingw-expand-absolute-user-path'
When compiling Git with a runtime prefix (so that it can be installed
into any location, finding its libexec/ directory relative to the
location of the `git` executable), it is convenient to provide
"absolute" Unix-y paths e.g. for http.sslCAInfo, and have those absolute
paths be resolved relative to the runtime prefix.

This patch makes it so for Windows. It is up for discussion whether we
want this for other platforms, too, as long as building with
RUNTIME_PREFIX.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:32 +02:00
Johannes Schindelin
aa03db8893 Merge branch 'file-url-to-unc-path'
This topic branch teaches Git to accept UNC paths of the form
file://host/share/repository.git.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:31 +02:00
Johannes Schindelin
1b94f4f907 Merge branch 'test-unc-fetch'
Fix fetching from UNC paths.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:31 +02:00
Johannes Schindelin
f467ae980f Merge branch 'drive-prefix'
This topic branch allows us to specify absolute paths without the drive
prefix e.g. when cloning.

Example:

	C:\Users\me> git clone https://github.com/git/git \upstream-git

This will clone into a new directory C:\upstream-git, in line with how
Windows interprets absolute paths.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:31 +02:00
Johannes Schindelin
76fb6d60f5 Merge pull request #996 from jeffhostetler/jeffhostetler/register_rename_src
diffcore-rename: speed up register_rename_src
2019-08-09 21:45:30 +02:00
Johannes Schindelin
6e84711abe Merge branch 'gitdir-at-unc-root'
This fixes a bug where a .git directory at the root of a network share
(e.g. \\MYSERVER\sharedfolder\.git) was not handled correctly.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:30 +02:00
Johannes Schindelin
19a5a62435 Merge 'fix-externals' into HEAD 2019-08-09 21:45:30 +02:00
Nathan Sanders
84c6ee33f6 mingw: cope with the Isilon network file system
On certain network filesystems (currently encounterd with Isilon, but in
theory more network storage solutions could be causing the same issue),
when the directory in question is missing, `raceproof_create_file()`
fails with an `ERROR_INVALID_PARAMETER` instead of an
`ERROR_PATH_NOT_FOUND`.

Since it is highly unlikely that we produce such an error by mistake
(the parameters we pass are fairly benign), we can be relatively certain
that the directory is missing in this instance. So let's just translate
that error automagically.

This fixes https://github.com/git-for-windows/git/issues/1345.

Signed-off-by: Nathan Sanders <spekbukkem@gmail.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:29 +02:00
Johannes Schindelin
652456f773 clean: remove mount points when possible
Windows' equivalent to "bind mounts", NTFS junction points, can be
unlinked without affecting the mount target. This is clearly what users
expect to happen when they call `git clean -dfx` in a worktree that
contains NTFS junction points: the junction should be removed, and the
target directory of said junction should be left alone (unless it is
inside the worktree).

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:29 +02:00
Johannes Schindelin
cf988bc865 Merge 'remote-hg-prerequisites' into HEAD
These fixes were necessary for Sverre Rabbelier's remote-hg to work,
but for some magic reason they are not necessary for the current
remote-hg. Makes you wonder how that one gets away with it.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:29 +02:00
Johannes Schindelin
798229341e clean: do not traverse mount points
It seems to be not exactly rare on Windows to install NTFS junction
points (the equivalent of "bind mounts" on Linux/Unix) in worktrees,
e.g. to map some development tools into a subdirectory.

In such a scenario, it is pretty horrible if `git clean -dfx` traverses
into the mapped directory and starts to "clean up".

Let's just not do that. Let's make sure before we traverse into a
directory that it is not a mount point (or junction).

This addresses https://github.com/git-for-windows/git/issues/607

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:29 +02:00
Johannes Schindelin
d0171823f3 Merge branch 'reset-stdin'
This topic branch adds the (experimental) --stdin/-z options to `git
reset`. Those patches are still under review in the upstream Git project,
but are already merged in their experimental form into Git for Windows'
`master` branch, in preparation for a MinGit-only release.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:29 +02:00
Johannes Schindelin
2587252d19 Build Python stuff with MSys2
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:28 +02:00
Johannes Schindelin
e8750a2517 Help debugging with MSys2 by optionally executing bash with strace
MSys2's strace facility is very useful for debugging... With this patch,
the bash will be executed through strace if the environment variable
GIT_STRACE_COMMANDS is set, which comes in real handy when investigating
issues in the test suite.

Also support passing a path to a log file via GIT_STRACE_COMMANDS to
force Git to call strace.exe with the `-o <path>` argument, i.e. to log
into a file rather than print the log directly.

That comes in handy when the output would otherwise misinterpreted by a
calling process as part of Git's output.

Note: the values "1", "yes" or "true" are *not* specifying paths, but
tell Git to let strace.exe log directly to the console.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:28 +02:00
Johannes Schindelin
e3f35ccb83 mingw: make is_hidden tests in t0001/t5611 more robust
We should not actually expect the first `attrib.exe` in the PATH to
be the one we are looking for. Or that it is in the PATH, for that
matter.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:28 +02:00
마누엘
df82e28a52 mingw: explicitly fflush stdout
For performance reasons `stdout` is buffered by default. That leads to
problems if after printing to `stdout` a read on `stdin` is performed.

For that reason interactive commands like `git clean -i` do not function
properly anymore if the `stdout` is not flushed by `fflush(stdout)` before
trying to read from `stdin`.

So let's precede all reads on `stdin` in `git clean -i` by flushing
`stdout`.

Signed-off-by: 마누엘 <nalla@hamal.uberspace.de>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:28 +02:00
Johannes Schindelin
8daf0f0afd t9001, t9116: avoid pipes
When grepping through the output of a command in the test suite, there
is always a chance that something goes wrong, in which case there would
not be anything useful to debug.

Let's redirect the output into a file instead, and grep that file, so
that the log can be inspected easily if the grep fails.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:28 +02:00
Johannes Schindelin
490ee9b82e gitk: prevent overly long command lines
To avoid running into command line limitations, some of Git's commands
support the `--stdin` option.

Let's use exactly this option in the three rev-list/log invocations in
gitk that would otherwise possibly run the danger of trying to invoke a
too-long command line.

While it is easy to redirect either stdin or stdout in Tcl/Tk scripts,
what we need here is both. We need to capture the output, yet we also
need to pipe in the revs/files arguments via stdin (because stdin does
not have any limit, unlike the command line). To help this, we use the
neat Tcl feature where you can capture stdout and at the same time feed
a fixed string as stdin to the spawned process.

One non-obvious aspect about this change is that the `--stdin` option
allows to specify revs, the double-dash, and files, but *no* other
options such as `--not`. This is addressed by prefixing the "negative"
revs with `^` explicitly rather than relying on the `--not` option
(thanks for coming up with that idea, Max!).

This fixes https://github.com/git-for-windows/git/issues/1987

Analysis-and-initial-patch-by: Max Kirillov <max@max630.net>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:28 +02:00
Johannes Schindelin
7e4593137b mingw: change core.fsyncObjectFiles = 1 by default
From the documentation of said setting:

	This boolean will enable fsync() when writing object files.

	This is a total waste of time and effort on a filesystem that
	orders data writes properly, but can be useful for filesystems
	that do not use journalling (traditional UNIX filesystems) or
	that only journal metadata and not file contents (OS X’s HFS+,
	or Linux ext3 with "data=writeback").

The most common file system on Windows (NTFS) does not guarantee that
order, therefore a sudden loss of power (or any other event causing an
unclean shutdown) would cause corrupt files (i.e. files filled with
NULs). Therefore we need to change the default.

Note that the documentation makes it sound as if this causes really bad
performance. In reality, writing loose objects is something that is done
only rarely, and only a handful of files at a time.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:28 +02:00
Johannes Schindelin
516a179006 Windows: add support for a Windows-wide configuration
Between the libgit2 and the Git for Windows project, there has been a
discussion how we could share Git configuration to avoid duplication (or
worse: skew).

Earlier, libgit2 was nice enough to just re-use Git for Windows'

	C:\Program Files (x86)\Git\etc\gitconfig

but with the upcoming Git for Windows 2.x, there would be more paths to
search, as we will have 64-bit and 32-bit versions, and the
corresponding config files will be in %PROGRAMFILES%\Git\mingw64\etc and
...\mingw32\etc, respectively.

Worse: there are portable Git for Windows versions out there which live
in totally unrelated directories, still.

Therefore we came to a consensus to use `%PROGRAMDATA%\Git\config` as the
location for shared Git settings that are of wider interest than just Git
for Windows.

Of course, the configuration in `%PROGRAMDATA%\Git\config` has the
widest reach, therefore it must take the lowest precedence, i.e. Git for
Windows can still override settings in its `etc/gitconfig` file.

Helped-by: Andreas Heiduk <asheiduk@gmail.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:27 +02:00
Johannes Schindelin
2abd2f91f9 ci: also test with MS Visual C on Azure Pipelines
... because we can, now.

We specifically reduce the number of parallel links for MSVC, as RAM
usage is an issue with MSVC's parallel mode, manifested in the symptom:

	fatal error LNK1318: Unexpected PDB error; OK (0) ''

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:27 +02:00
Johannes Schindelin
1a81b5c7fe ci: really use shallow clones on Azure Pipelines
This was a left-over from the previous YAML schema, and it no longer
works. The problem was noticed while editing `azure-pipelines.yml` in VS
Code with the very helpful "Azure Pipelines" extension (syntax
highlighting and intellisense for `azure-pipelines.yml`...).

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:27 +02:00
Johannes Schindelin
50fa1b80dc msvc: work around a bug in GetEnvironmentVariable()
The return value of that function is 0 both for variables that are
unset, as well as for variables whose values are empty. To discern those
two cases, one has to call `GetLastError()`, whose return value is
`ERROR_ENVVAR_NOT_FOUND` and `ERROR_SUCCESS`, respectively.

Except that it is not actually set to `ERROR_SUCCESS` in the latter
case, apparently, but the last error value seems to be simply unchanged.

To work around this, let's just re-set the last error value just before
inspecting the environment variable.

This fixes a problem that triggers failures in t3301-notes.sh (where we
try to override config settings by passing empty values for certain
environment variables).

This problem is hidden in the MINGW build by the fact that older
MSVC runtimes (such as the one used by MINGW builds) have a `calloc()`
that re-sets the last error value in case of success, while newer
runtimes set the error value only if `NULL` is returned by that
function.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
2019-08-09 21:45:27 +02:00