If we use the default system reader FileStoreAttributes cannot persist
attributes in userConfig when tests run in Bazel due to sandboxing.
Hence we need to ensure that all tests use MockSystemReader (and
especially a mocked userConfig).

Change-Id: Ic1ad8e2ec5a150c5433434a5f6667d6c4674c87d
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

To enable persisting the minimal racy threshold per FileStore add a
new config option to the user global git configuration:

- Config section is "filesystem"
- Config subsection is concatenation of
  - Java vendor (system property "java.vendor")
  - Java version (system property "java.version")
  - FileStore's name, on Windows we use the attribute volume:vsn instead
    since  the name is not necessarily unique.
  - separated by '|'
  e.g.
    "AdoptOpenJDK|1.8.0_212-b03|/dev/disk1s1"
  The same prefix is used as for filesystem timestamp resolution, so
  both values are stored in the same config section
- The config key for minmal racy threshold is "minRacyThreshold" as a
  time value, supported time units are those supported by
  DefaultTypedConfigGetter#getTimeUnit
- measure for 3 seconds to limit runtime which depends on hardware, OS
  and Java version being used

If the minimal racy threshold is configured for a given FileStore the
configured value is used instead of measuring it.

When the minimal racy threshold was measured it is persisted in the user
global git configuration.

Rename FileStoreAttributeCache to FileStoreAttributes since this class
is now declared public in order to enable exposing all attributes in one
object.

Example:

[filesystem "AdoptOpenJDK|11.0.3|/dev/disk1s1"]
	timestampResolution = 7000 nanoseconds
	minRacyThreshold = 3440 microseconds

Change-Id: I22195e488453aae8d011b0a8e3276fe3d99deaea
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
Also-By: Marc Strapetz <marc.strapetz@syntevo.com>

By running FileSnapshotTest#detectFileModified we found that the sum of
measured filesystem timestamp resolution and measured clock resolution
may yield a too small interval after a file has been modified which we
need to consider racily clean. In our tests we didn't find this behavior
on all systems we tested on, e.g. on MacOS using APFS and Java 8 and 11
this effect was not observed.

On Linux (SLES 15, kernel 4.12.14-150.22-default) we collected the
following test results using Java 8 and 11:

In 23-98% of 10000 test runs (depending on filesystem type and Java
version) the test failed, which means the effective interval which needs
to be considered racily clean after a file was modified is larger than
the measured file timestamp resolution.

"delta" is the observed interval after a file has been modified but
FileSnapshot did not yet detect the modification:

"resolution" is the measured sum of file timestamp resolution and clock
resolution seen in Java.

Java version    filesystem  failures resolution  min delta   max delta
1.8.0_212-b04   btrfs	    98.6%       1 ms        3.6 ms      6.6 ms
1.8.0_212-b04   ext4        82.6%       3 ms        1.1 ms      4.1 ms
1.8.0_212-b04   xfs         23.8%       4 ms        3.7 ms      3.9 ms
1.8.0_212-b04   zfs         23.1%       3 ms        4.8 ms      5.0 ms
11.0.3+7        btrfs       98.1%       3 us        0.7 ms      4.7 ms
11.0.3+7        ext4        98.1%       6 us        0.7 ms      4.7 ms
11.0.3+7        xfs         98.5%       7 us        0.1 ms      8.0 ms
11.0.3+7        zfs         98.4%       7 us        0.7 ms      5.2 ms

Mac OS
1.8.0_212       APFS        0%          1 s
11.0.3+7        APFS        0%          6 us

The observed delta is not distributed according to a normal gaussian
distribution but rather random in the observed range between "min delta"
and "max delta".

Run this test after measuring file timestamp resolution in
FS.FileAttributeCache to auto-configure JGit since it's unclear what
mechanism is causing this effect.

In FileSnapshot#isRacyClean use the maximum of the measured timestamp
resolution and the measured "delta" as explained above to decide if a
given FileSnapshot is to be considered racily clean. Add a 30% safety
margin to ensure we are on the safe side.

Change-Id: I1c8bb59f6486f174b7bbdc63072777ddbe06694d
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

Change-Id: I304b2b6f2e39f72f620bba53aead60256aed3660
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

This helps to avoid some time critical tests can't prepare the test
fixture intended since measuring timestamp resolution takes time.

Change-Id: Ib34023e682a106070ca97e98ef16789a4dfb97b4
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

- use Path instead of File
- create test directories, files and output stream using Files methods
- delete unused list "files"

Change-Id: I8c5c601eca9f613efb5618d33b262277df92a06a
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

Change-Id: I3b748620f067582afef20f144feebe40d0332be2
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

Change-Id: I6714fc3666e1bced22abba94ceb700477349586e
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

Change-Id: Id4c49d4af30bcc5210d35630a8699574694060bb
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

Instead of hard-coding the charset strings "US-ASCII", "UTF-8", and
"ISO-8859-1", use the corresponding constants from StandardCharsets.

UnsupportedEncodingException is not thrown when the StandardCharset
constants are used, so remove the now redundant handling.

Because the encoding names are no longer hard-coded strings, also
remove redundant $NON-NLS warning suppressions.

Also replace existing usages of the constants with static imports.

Change-Id: I0a4510d3d992db5e277f009a41434276f95bda4e
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

ConfigTest#pathToString is not visible to FileBasedConfigTest when
bulding with bazel.

Move it to FileUtils rather than messing about with the bazel build
rules to make it visible.

Change-Id: Idcfd4822699dac9dc4a426088a929a9cd31bf53f
Signed-off-by: David Pursehouse <david.pursehouse@gmail.com>

Relative include.path are now resolved against the config's parent
directory. include.path starting with ~/ are resolved against the
user's home directory

Change-Id: I91911ef404126618b1ddd3589294824a0ad919e6
Signed-off-by: Marc Strapetz <marc.strapetz@syntevo.com>

Buck does not create a target directory for the build output, this
is Maven specific and the project unit tests should not rely on it.

Instead follow the pattern used by org.eclipse.jgit.test which is to
create a temporary directory in the system temporary folder, and
configure the Maven surefire plugin to use the target directory.

Change-Id: Iebe5093332343a90f51080614e083aac0d29c26d

Also cleanup wildcards in import statements.

Change-Id: I28c1435ae7482de1209aeefc755a230ef5b8c15d
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

Change-Id: I1f5dc07182dbf6bba2a9f4807fdd25b475da4ead