0d9b0d7885
The five tests checking 'git fast-import's checkpoint handling in
't9300-fast-import.sh', all with the prefix "V:" in their test
description, can hang indefinitely if 'git fast-import' unexpectedly
dies early in any of these tests.
These five tests run 'git fast-import' in the background, while
feeding instructions to its standard input through a fifo (fd 8) from
a background subshell, and reading and verifying its standard output
through another fifo (fd 9) in the test script's main shell process.
This "reading and verifying" is basically a 'while read ...' shell
loop iterating until 'git fast-import' outputs the expected line,
ignoring any other output. This doesn't work very well when 'git
fast-import' dies before printing that particular line, because the
'read' builtin doesn't get EOF after the death of 'git fast-import',
as their input and output are not connected directly but through a
fifo. Consequently, that 'read' hangs waiting for the next line from
the already dead 'git fast-import', leaving the test script and in
turn the whole test suite hanging.
Avoid this hang by checking whether the background 'git fast-import'
process exited unexpectedly early, and interrupt the 'while read' loop
if it did. We have to jump through some hoops to achive that, though:
- Start the background 'git fast-import' in another background
subshell, which then:
- prints the PID of that 'git fast-import' process to the fifo,
to be read by the main shell process, so it will know which
process to kill when the test is finished.
- waits until that 'git fast-import' process exits. If it does
exit, then report its exit code, and write a message to the
fifo used for 'git fast-import's standard output, thus
un-block the 'read' builtin in the main shell process.
- Modify that 'while read' loop to break the loop upon seeing that
message, and fail the test in the usual way.
- Once the test is finished kill that background subshell as well,
and do so before killing the background 'git fast-import'.
Otherwise the background 'git fast-import' and subshell processes
would die racily, and if 'git fast-import' were to die sooner,
then we might get some undesired and potentially confusing
messages in the test's output.
Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Git - fast, scalable, distributed revision control system
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