While cron is specified by POSIX, there are a wide variety of
implementations in use. "git maintenance" assumes that the
"crontab" command can be fed from its standard input the new
contents and the syntax to do so is not to have any filename
argument, as POSIX describes. However, on FreeBSD, the cron
implementation requires a file name argument: if the user wants to
edit standard input, they must specify "-".
Unfortunately, POSIX systems do not have to interpret "-" on the
command line of crontab as a request to read from the standard
input. Blindly adding "-" on the command line would not work as a
general solution.
Since POSIX tells us that cron must accept a file name argument, let's
solve this problem by specifying a temporary file instead. This will
ensure that we work with the vast majority of implementations.
Note that because delete_tempfile closes the file for us, we should not
call fclose here on the handle, since doing so will introduce a double
free.
Reported-by: Renato Botelho <garga@FreeBSD.org>
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add new subcommands to 'git maintenance' that start or stop background
maintenance using 'cron', when available. This integration is as simple
as I could make it, barring some implementation complications.
The schedule is laid out as follows:
0 1-23 * * * $cmd maintenance run --schedule=hourly
0 0 * * 1-6 $cmd maintenance run --schedule=daily
0 0 * * 0 $cmd maintenance run --schedule=weekly
where $cmd is a properly-qualified 'git for-each-repo' execution:
$cmd=$path/git --exec-path=$path for-each-repo --config=maintenance.repo
where $path points to the location of the Git executable running 'git
maintenance start'. This is critical for systems with multiple versions
of Git. Specifically, macOS has a system version at '/usr/bin/git' while
the version that users can install resides at '/usr/local/bin/git'
(symlinked to '/usr/local/libexec/git-core/git'). This will also use
your locally-built version if you build and run this in your development
environment without installing first.
This conditional schedule avoids having cron launch multiple 'git
for-each-repo' commands in parallel. Such parallel commands would likely
lead to the 'hourly' and 'daily' tasks competing over the object
database lock. This could lead to to some tasks never being run! Since
the --schedule=<frequency> argument will run all tasks with _at least_
the given frequency, the daily runs will also run the hourly tasks.
Similarly, the weekly runs will also run the daily and hourly tasks.
The GIT_TEST_CRONTAB environment variable is not intended for users to
edit, but instead as a way to mock the 'crontab [-l]' command. This
variable is set in test-lib.sh to avoid a future test from accidentally
running anything with the cron integration from modifying the user's
schedule. We use GIT_TEST_CRONTAB='test-tool crontab <file>' in our
tests to check how the schedule is modified in 'git maintenance
(start|stop)' commands.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
