git/run-command.c, branch v2.5.2

vreportf: report to arbitrary filehandles

2015-08-11T21:24:50Z

The vreportf function always goes to stderr, but run-command wants child errors to go to the parent's original stderr. To solve this, commit a5487dd duplicates the stderr fd and installs die and error handlers to direct the output appropriately (which later turned into the vwritef function). This has two downsides, though: - we make multiple calls to write(), which contradicts the "write at once" logic from d048a96 (print warning/error/fatal messages in one shot, 2007-11-09). - the custom handlers basically duplicate the normal handlers. They're only a few lines of code, but we should not have to repeat the magic "exit(128)", for example. We can solve the first by using fdopen() on the duplicated descriptor. We can't pass this to vreportf, but we could introduce a new vreportf_to to handle it. However, to fix the second problem, we instead introduce a new "set_error_handle" function, which lets the normal vreportf calls output to a handle besides stderr. Thus we can get rid of our custom handlers entirely, and just ask the regular handlers to output to our new descriptor. And as vwritef has no more callers, it can just go away. Signed-off-by: Jeff King Signed-off-by: Junio C Hamano

Merge branch 'nd/multiple-work-trees'

2015-05-11T21:23:39Z

A replacement for contrib/workdir/git-new-workdir that does not rely on symbolic links and make sharing of objects and refs safer by making the borrowee and borrowers aware of each other. * nd/multiple-work-trees: (41 commits) prune --worktrees: fix expire vs worktree existence condition t1501: fix test with split index t2026: fix broken &&-chain t2026 needs procondition SANITY git-checkout.txt: a note about multiple checkout support for submodules checkout: add --ignore-other-wortrees checkout: pass whole struct to parse_branchname_arg instead of individual flags git-common-dir: make "modules/" per-working-directory directory checkout: do not fail if target is an empty directory t2025: add a test to make sure grafts is working from a linked checkout checkout: don't require a work tree when checking out into a new one git_path(): keep "info/sparse-checkout" per work-tree count-objects: report unused files in $GIT_DIR/worktrees/... gc: support prune --worktrees gc: factor out gc.pruneexpire parsing code gc: style change -- no SP before closing parenthesis checkout: clean up half-prepared directories in --to mode checkout: reject if the branch is already checked out elsewhere prune: strategies for linked checkouts checkout: support checking out into a new working directory ...

Merge branch 'jk/run-command-capture'

2015-03-25T19:54:27Z

The run-command interface was easy to abuse and make a pipe for us to read from the process, wait for the process to finish and then attempt to read its output, which is a pattern that lead to a deadlock. Fix such uses by introducing a helper to do this correctly (i.e. we need to read first and then wait the process to finish) and also add code to prevent such abuse in the run-command helper. * jk/run-command-capture: run-command: forbid using run_command with piped output trailer: use capture_command submodule: use capture_command wt-status: use capture_command run-command: introduce capture_command helper wt_status: fix signedness mismatch in strbuf_read call wt-status: don't flush before running "submodule status"

run-command: forbid using run_command with piped output

2015-03-23T04:39:22Z

Because run_command both spawns and wait()s for the command before returning control to the caller, any reads from the pipes we open must necessarily happen after wait() returns. This can lead to deadlock, as the child process may block on writing to us while we are blocked waiting for it to exit. Worse, it only happens when the child fills the pipe buffer, which means that the problem may come and go depending on the platform and the size of the output produced by the child. Let's detect and flag this dangerous construct so that we can catch potential bugs early in the test suite rather than having them happen in the field. Signed-off-by: Jeff King Signed-off-by: Junio C Hamano

run-command: introduce capture_command helper

2015-03-23T04:38:31Z

Something as simple as reading the stdout from a command turns out to be rather hard to do right. Doing: cmd.out = -1; run_command(&cmd); strbuf_read(&buf, cmd.out, 0); can result in deadlock if the child process produces a large amount of output. What happens is: 1. The parent spawns the child with its stdout connected to a pipe, of which the parent is the sole reader. 2. The parent calls wait(), blocking until the child exits. 3. The child writes to stdout. If it writes more data than the OS pipe buffer can hold, the write() call will block. This is a deadlock; the parent is waiting for the child to exit, and the child is waiting for the parent to call read(). So we might try instead: start_command(&cmd); strbuf_read(&buf, cmd.out, 0); finish_command(&cmd); But that is not quite right either. We are examining cmd.out and running finish_command whether start_command succeeded or not, which is wrong. Moreover, these snippets do not do any error handling. If our read() fails, we must make sure to still call finish_command (to reap the child process). And both snippets failed to close the cmd.out descriptor, which they must do (provided start_command succeeded). Let's introduce a run-command helper that can make this a bit simpler for callers to get right. Signed-off-by: Jeff King Signed-off-by: Junio C Hamano

git-compat-util.h: move SHELL_PATH default into header

2015-03-10T22:11:24Z

If SHELL_PATH is not defined we use "/bin/sh". However, run-command.c is not the only file that needs to use the default value so move it into a common header. Signed-off-by: Kyle J. McKay Signed-off-by: Junio C Hamano

Merge branch 'jc/hook-cleanup'

2014-12-22T20:27:10Z

Remove unused code. * jc/hook-cleanup: run-command.c: retire unused run_hook_with_custom_index()

path.c: make get_pathname() call sites return const char *

2014-12-01T19:00:10Z

Before the previous commit, get_pathname returns an array of PATH_MAX length. Even if git_path() and similar functions does not use the whole array, git_path() caller can, in theory. After the commit, get_pathname() may return a buffer that has just enough room for the returned string and git_path() caller should never write beyond that. Make git_path(), mkpath() and git_path_submodule() return a const buffer to make sure callers do not write in it at all. This could have been part of the previous commit, but the "const" conversion is too much distraction from the core changes in path.c. Signed-off-by: Nguyễn Thái Ngọc Duy Signed-off-by: Junio C Hamano

run-command.c: retire unused run_hook_with_custom_index()

2014-12-01T16:39:43Z

This was originally meant to be used to rewrite run_commit_hook() that only special cases the GIT_INDEX_FILE environment, but the run_hook_ve() refactoring done earlier made the implementation of run_commit_hook() thin and clean enough. Nobody uses this, so retire it as an unfinished clean-up made unnecessary. Signed-off-by: Junio C Hamano

run-command: use void to declare that functions take no parameters

2014-11-10T22:43:19Z

Explicitly declare that git_atexit_dispatch() and git_atexit_clear() take no parameters instead of leaving their parameter list empty and thus unspecified. Signed-off-by: Rene Scharfe Signed-off-by: Junio C Hamano