git/git.c, branch v2.11.4

execv_dashed_external: wait for child on signal death

2017-01-09T21:41:40Z

When you hit ^C to interrupt a git command going to a pager, this usually leaves the pager running. But when a dashed external is in use, the pager ends up in a funny state and quits (but only after eating one more character from the terminal!). This fixes it. Explaining the reason will require a little background. When git runs a pager, it's important for the git process to hang around and wait for the pager to finish, even though it has no more data to feed it. This is because git spawns the pager as a child, and thus the git process is the session leader on the terminal. After it dies, the pager will finish its current read from the terminal (eating the one character), and then get EIO trying to read again. When you hit ^C, that sends SIGINT to git and to the pager, and it's a similar situation. The pager ignores it, but the git process needs to hang around until the pager is done. We addressed that long ago in a3da882120 (pager: do wait_for_pager on signal death, 2009-01-22). But when you have a dashed external (or an alias pointing to a builtin, which will re-exec git for the builtin), there's an extra process in the mix. For instance, running: $ git -c alias.l=log l will end up with a process tree like: git (parent) \ git-log (child) \ less (pager) If you hit ^C, SIGINT goes to all of them. The pager ignores it, and the child git process will end up in wait_for_pager(). But the parent git process will die, and the usual EIO trouble happens. So we really want the parent git process to wait_for_pager(), but of course it doesn't know anything about the pager at all, since it was started by the child. However, we can have it wait on the git-log child, which in turn is waiting on the pager. And that's what this patch does. There are a few design decisions here worth explaining: 1. The new feature is attached to run-command's clean_on_exit feature. Partly this is convenience, since that feature already has a signal handler that deals with child cleanup. But it's also a meaningful connection. The main reason that dashed externals use clean_on_exit is to bind the two processes together. If somebody kills the parent with a signal, we propagate that to the child (in this instance with SIGINT, we do propagate but it doesn't matter because the original signal went to the whole process group). Likewise, we do not want the parent to go away until the child has done so. In a traditional Unix world, we'd probably accomplish this binding by just having the parent execve() the child directly. But since that doesn't work on Windows, everything goes through run_command's more spawn-like interface. 2. We do _not_ automatically waitpid() on any clean_on_exit children. For dashed externals this makes sense; we know that the parent is doing nothing but waiting for the child to exit anyway. But with other children, it's possible that the child, after getting the signal, could be waiting on the parent to do something (like closing a descriptor). If we were to wait on such a child, we'd end up in a deadlock. So this errs on the side of caution, and lets callers enable the feature explicitly. 3. When we send children the cleanup signal, we send all the signals first, before waiting on any children. This is to avoid the case where one child might be waiting on another one to exit, causing a deadlock. We inform all of them that it's time to die before reaping any. In practice, there is only ever one dashed external run from a given process, so this doesn't matter much now. But it future-proofs us if other callers start using the wait_after_clean mechanism. There's no automated test here, because it would end up racy and unportable. But it's easy to reproduce the situation by running the log command given above and hitting ^C. Signed-off-by: Jeff King Signed-off-by: Junio C Hamano

execv_dashed_external: stop exiting with negative code

2017-01-09T21:41:35Z

When we try to exec a git sub-command, we pass along the status code from run_command(). But that may return -1 if we ran into an error with pipe() or execve(). This tends to work (and end up as 255 due to twos-complement wraparound and truncation), but in general it's probably a good idea to avoid negative exit codes for portability. We can easily translate to the normal generic "128" code we get when syscalls cause us to die. Signed-off-by: Jeff King Signed-off-by: Junio C Hamano

execv_dashed_external: use child_process struct

2017-01-09T21:41:33Z

When we run a dashed external, we use the one-liner run_command_v_opt() to do so. Let's switch to using a child_process struct, which has two advantages: 1. We can drop all of the allocation and cleanup code for building our custom argv array, and just rely on the builtin argv_array (at the minor cost of doing a few extra mallocs). 2. We have access to the complete range of child_process options, not just the ones that the "_opt()" form can forward. Signed-off-by: Jeff King Signed-off-by: Junio C Hamano

Merge branch 'jk/common-main'

2016-11-29T20:22:13Z

Fix for a small regression in a topic already in 'master'. * jk/common-main: common-main: stop munging argv[0] path

common-main: stop munging argv[0] path

2016-11-29T19:01:48Z

Since 650c44925 (common-main: call git_extract_argv0_path(), 2016-07-01), the argv[0] that is seen in cmd_main() of individual programs is always the basename of the executable, as common-main strips off the full path. This can produce confusing results for git-daemon, which wants to re-exec itself. For instance, if the program was originally run as "/usr/lib/git/git-daemon", it will try just re-execing "git-daemon", which will find the first instance in $PATH. If git's exec-path has not been prepended to $PATH, we may find the git-daemon from a different version (or no git-daemon at all). Normally this isn't a problem. Git commands are run as "git daemon", the git wrapper puts the exec-path at the front of $PATH, and argv[0] is already "daemon" anyway. But running git-daemon via its full exec-path, while not really a recommended method, did work prior to 650c44925. Let's make it work again. The real goal of 650c44925 was not to munge argv[0], but to reliably set the argv0_path global. The only reason it munges at all is that one caller, the git.c wrapper, piggy-backed on that computation to find the command basename. Instead, let's leave argv[0] untouched in common-main, and have git.c do its own basename computation. While we're at it, let's drop the return value from git_extract_argv0_path(). It was only ever used in this one callsite, and its dual purposes is what led to this confusion in the first place. Note that by changing the interface, the compiler can confirm for us that there are no other callers storing the return value. But the compiler can't tell us whether any of the cmd_main() functions (besides git.c) were relying on the basename munging. However, we can observe that prior to 650c44925, no other cmd_main() functions did that munging, and no new cmd_main() functions have been introduced since then. So we can't be regressing any of those cases. Signed-off-by: Jeff King Signed-off-by: Junio C Hamano

archive: read local configuration

2016-11-22T21:55:20Z

Since b9605bc4f2 ("config: only read .git/config from configured repos", 2016-09-12), we do not read from ".git/config" unless we know we are in a repository. "git archive" however didn't do the repository discovery and instead relied on the old behaviour. Teach the command to run a "gentle" version of repository discovery so that local configuration variables are honoured. [jc: stole tests from peff] Signed-off-by: Junio C Hamano

mailinfo: read local configuration

2016-11-22T21:13:16Z

Since b9605bc4f2 ("config: only read .git/config from configured repos", 2016-09-12), we do not read from ".git/config" unless we know we are in a repository. "git mailinfo" however didn't do the repository discovery and instead relied on the old behaviour. This was mostly OK because it was merely run as a helper program by other porcelain scripts that first chdir's up to the root of the working tree. Teach the command to run a "gentle" version of repository discovery so that local configuration variables like mailinfo.scissors are honoured. Signed-off-by: Junio C Hamano

Merge branch 'jc/cocci-xstrdup-or-null'

2016-10-26T20:14:45Z

Code cleanup. * jc/cocci-xstrdup-or-null: cocci: refactor common patterns to use xstrdup_or_null()

Merge branch 'bw/ls-files-recurse-submodules'

2016-10-26T20:14:44Z

"git ls-files" learned "--recurse-submodules" option that can be used to get a listing of tracked files across submodules (i.e. this only works with "--cached" option, not for listing untracked or ignored files). This would be a useful tool to sit on the upstream side of a pipe that is read with xargs to work on all working tree files from the top-level superproject. * bw/ls-files-recurse-submodules: ls-files: add pathspec matching for submodules ls-files: pass through safe options for --recurse-submodules ls-files: optionally recurse into submodules git: make super-prefix option

cocci: refactor common patterns to use xstrdup_or_null()

2016-10-12T18:22:10Z

d64ea0f83b ("git-compat-util: add xstrdup_or_null helper", 2015-01-12) added a handy wrapper that allows us to get a duplicate of a string or NULL if the original is NULL, but a handful of codepath predate its introduction or just weren't aware of it. Signed-off-by: Junio C Hamano