In the codepath that comes up with the hostname to be used in an
e-mail when the user didn't tell us, we looked at ai_canonname
field in struct addrinfo without making sure it is not NULL first.

* jk/ident-ai-canonname-could-be-null:
  ident: handle NULL ai_canonname

We call getaddrinfo() to try to convert a short hostname
into a fully-qualified one (to use it as an email domain).
If there isn't a canonical name, getaddrinfo() will
generally return either a NULL addrinfo list, or one in
which ai->ai_canonname is a copy of the original name.

However, if the result of gethostname() looks like an IP
address, then getaddrinfo() behaves differently on some
systems. On OS X, it will return a "struct addrinfo" with a
NULL ai_canonname, and we segfault feeding it to strchr().

This is hard to test reliably because it involves not only a
system where we we have to fallback to gethostname() to come
up with an ident, but also where the hostname is a number
with no dots. But I was able to replicate the bug by faking
a hostname, like:

    diff --git a/ident.c b/ident.c
    index e20a772..b790d28 100644
    --- a/ident.c
    +++ b/ident.c
    @@ -128,6 +128,7 @@ static void add_domainname(struct strbuf *out, int *is_bogus)
                     *is_bogus = 1;
                     return;
             }
    +        xsnprintf(buf, sizeof(buf), "1");
             if (strchr(buf, '.'))
                     strbuf_addstr(out, buf);
             else if (canonical_name(buf, out) < 0) {

and running "git var GIT_AUTHOR_IDENT" on an OS X system.

Before this patch it segfaults, and after we correctly
complain of the bogus "user@1.(none)" address (though this
bogus address would be suitable for non-object uses like
writing reflogs).

Reported-by: Jonas Thiel <jonas.lierschied@gmx.de>
Diagnosed-by: John Keeping <john@keeping.me.uk>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Not-so-recent rewrite of "git am" that started making internal
calls into the commit machinery had an unintended regression, in
that no matter how many seconds it took to apply many patches, the
resulting committer timestamp for the resulting commits were all
the same.

* jk/reset-ident-time-per-commit:
  am: reset cached ident date for each patch

When we compute the date to go in author/committer lines of
commits, or tagger lines of tags, we get the current date
once and then cache it for the rest of the program.  This is
a good thing in some cases, like "git commit", because it
means we do not racily assign different times to the
author/committer fields of a single commit object.

But as more programs start to make many commits in a single
process (e.g., the recently builtin "git am"), it means that
you'll get long strings of commits with identical committer
timestamps (whereas before, we invoked "git commit" many
times and got true timestamps).

This patch addresses it by letting callers reset the cached
time, which means they'll get a fresh time on their next
call to git_committer_info() or git_author_info(). The first
caller to do so is "git am", which resets the time for each
patch it applies.

It would be nice if we could just do this automatically
before filling in the ident fields of commit and tag
objects. Unfortunately, it's hard to know where a particular
logical operation begins and ends.

For instance, if commit_tree_extended() were to call
reset_ident_date() before getting the committer/author
ident, that doesn't quite work; sometimes the author info is
passed in to us as a parameter, and it may or may not have
come from a previous call to ident_default_date(). So in
those cases, we lose the property that the committer and the
author timestamp always match.

You could similarly put a date-reset at the end of
commit_tree_extended(). That actually works in the current
code base, but it's fragile. It makes the assumption that
after commit_tree_extended() finishes, the caller has no
other operations that would logically want to fall into the
same timestamp.

So instead we provide the tool to easily do the reset, and
let the high-level callers use it to annotate their own
logical operations.

There's no automated test, because it would be inherently
racy (it depends on whether the program takes multiple
seconds to run). But you can see the effect with something
like:

  # make a fake 100-patch series
  top=$(git rev-parse HEAD)
  bottom=$(git rev-list --first-parent -100 HEAD | tail -n 1)
  git log --format=email --reverse --first-parent \
          --binary -m -p $bottom..$top >patch

  # now apply it; this presumably takes multiple seconds
  git checkout --detach $bottom
  git am <patch

  # now count the number of distinct committer times;
  # prior to this patch, there would only be one, but
  # now we'd typically see several.
  git log --format=%ct $bottom.. | sort -u

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Helped-by: Paul Tan <pyokagan@gmail.com>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

The "user.useConfigOnly" configuration variable makes it an error
if users do not explicitly set user.name and user.email.  However,
its check was not done early enough and allowed another error to
trigger, reporting that the default value we guessed from the
system setting was unusable.  This was a suboptimal end-user
experience as we want the users to set user.name/user.email without
relying on the auto-detection at all.

* da/user-useconfigonly:
  ident: give "please tell me" message upon useConfigOnly error
  ident: check for useConfigOnly before auto-detection of name/email

The code for warning_errno/die_errno has been refactored and a new
error_errno() reporting helper is introduced.

* nd/error-errno: (41 commits)
  wrapper.c: use warning_errno()
  vcs-svn: use error_errno()
  upload-pack.c: use error_errno()
  unpack-trees.c: use error_errno()
  transport-helper.c: use error_errno()
  sha1_file.c: use {error,die,warning}_errno()
  server-info.c: use error_errno()
  sequencer.c: use error_errno()
  run-command.c: use error_errno()
  rerere.c: use error_errno() and warning_errno()
  reachable.c: use error_errno()
  mailmap.c: use error_errno()
  ident.c: use warning_errno()
  http.c: use error_errno() and warning_errno()
  grep.c: use error_errno()
  gpg-interface.c: use error_errno()
  fast-import.c: use error_errno()
  entry.c: use error_errno()
  editor.c: use error_errno()
  diff-no-index.c: use error_errno()
  ...

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

The "user.useConfigOnly" configuration variable makes it an error
if users do not explicitly set user.name and user.email.  However,
its check was not done early enough and allowed another error to
trigger, reporting that the default value we guessed from the
system setting was unusable.  This was a suboptimal end-user
experience as we want the users to set user.name/user.email without
relying on the auto-detection at all.

* da/user-useconfigonly:
  ident: give "please tell me" message upon useConfigOnly error
  ident: check for useConfigOnly before auto-detection of name/email

The env_hint message applies perfectly to the case when
user.useConfigOnly is set and at least one of the user.name and the
user.email are not provided.

Additionally, use a less descriptive error message to discourage
users from disabling user.useConfigOnly configuration variable to
work around this error condition.  We want to encourage them to set
user.name or user.email instead.

Signed-off-by: Marios Titas <redneb@gmx.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

If user.useConfigOnly is set, it does not make sense to try to
auto-detect the name and/or the email.  The auto-detection may
even result in a bogus name and trigger an error message.

Check if the use-config-only is set and die if no explicit name was
given, before attempting to auto-detect, to correct this.

Signed-off-by: Marios Titas <redneb@gmx.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>