Pushing a non-fast-forward update to a remote repository will result in
an error, but the hint text doesn't provide the correct resolution in
every case. Give better resolution advice in three push scenarios:

1) If you push your current branch and it triggers a non-fast-forward
error, you should merge remote changes with 'git pull' before pushing
again.

2) If you push to a shared repository others push to, and your local
tracking branches are not kept up to date, the 'matching refs' default
will generate non-fast-forward errors on outdated branches. If this is
your workflow, the 'matching refs' default is not for you. Consider
setting the 'push.default' configuration variable to 'current' or
'upstream' to ensure only your current branch is pushed.

3) If you explicitly specify a ref that is not your current branch or
push matching branches with ':', you will generate a non-fast-forward
error if any pushed branch tip is out of date. You should checkout the
offending branch and merge remote changes before pushing again.

Teach transport.c to recognize these scenarios and configure push.c
to hint for them. If 'git push's default behavior changes or we
discover more scenarios, extension is easy. Standardize on the
advice API and add three new advice variables, 'pushNonFFCurrent',
'pushNonFFDefault', and 'pushNonFFMatching'. Setting any of these
to 'false' will disable their affiliated advice. Setting
'pushNonFastForward' to false will disable all three, thus preserving the
config option for users who already set it, but guaranteeing new
users won't disable push advice accidentally.
Based-on-patch-by: NJunio C Hamano <gitster@pobox.com>
Signed-off-by: NChristopher Tiwald <christiwald@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

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

Enable future callers to report a conflict and not die immediately by
introducing a new function called error_resolve_conflict.
Re-implement die_resolve_conflict as a call to error_resolve_conflict
followed by a call to die.  Consequently, the message printed by
die_resolve_conflict changes from

  fatal: 'commit' is not possible because you have unmerged files.
         Please, fix them up in the work tree ...
         ...

to

  error: 'commit' is not possible because you have unmerged files.
  hint: Fix them up in the work tree ...
  hint: ...
  fatal: Exiting because of an unresolved conflict.

Hints are printed using the same advise function introduced in
v1.7.3-rc0~26^2~3 (Introduce advise() to print hints, 2010-08-11).
Inspired-by: NChristian Couder <chistian.couder@gmail.com>
Helped-by: NJonathan Nieder <jrnieder@gmail.com>
Reviewed-by: NJonathan Nieder <jrnieder@gmail.com>
Signed-off-by: NRamkumar Ramachandra <artagnon@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

The old "advice" message explained how to create a branch after going into
a detached HEAD state but didn't make it clear why the user may want to do
so.  Also "moving to ... which isn't a local branch" was unclear if it is
complaining, if it is describing the new state, or if it is explaining why
the HEAD is detached (the true reason is the last one).

Give the established phrase 'detached HEAD' first to make it easy for
users to look up the concept in documentation, and briefly describe what
can be done in the state (i.e. play around without having to clean up)
before telling the user how to keep what was done during the temporary
state.

Allow the long description to be hidden by setting advice.detachedHead
configuration to false.

We might want to customize the advice depending on how the commit to check
out was spelled (e.g. instead of "new-branch-name", we way want to say
"topic" when "git checkout origin/topic" triggered this message) in later
updates, but this encapsulates that into a separate function and it should
be a good first step.
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

We now nag the user with a giant warning when their identity
was pulled from the username, hostname, and gecos
information, in case it is not correct. Most users will
suppress this by simply setting up their information
correctly.

However, there may be some users who consciously want to use
that information, because having the value change from host
to host contains useful information. These users can now set
advice.implicitidentity to false to suppress the message.
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Various commands refuse to run in the presence of conflicts (commit,
merge, pull, cherry-pick/revert). They all used to provide rough, and
inconsistant error messages.

A new variable advice.resolveconflict is introduced, and allows more
verbose messages, pointing the user to the appropriate solution.

For commit, the error message used to look like this:

$ git commit
foo.txt: needs merge
foo.txt: unmerged (c34a92682e0394bc0d6f4d4a67a8e2d32395c169)
foo.txt: unmerged (3afcd75de8de0bb5076942fcb17446be50451030)
foo.txt: unmerged (c9785d77b76dfe4fb038bf927ee518f6ae45ede4)
error: Error building trees

The "need merge" line is given by refresh_cache. We add the IN_PORCELAIN
option to make the output more consistant with the other porcelain
commands, and catch the error in return, to stop with a clean error
message. The next lines were displayed by a call to cache_tree_update(),
which is not reached anymore if we noticed the conflict.

The new output looks like:

U       foo.txt
fatal: 'commit' is not possible because you have unmerged files.
Please, fix them up in the work tree, and then use 'git add/rm <file>' as
appropriate to mark resolution and make a commit, or use 'git commit -a'.

Pull is slightly modified to abort immediately if $GIT_DIR/MERGE_HEAD
exists instead of waiting for merge to complain.

The behavior of merge and the test-case are slightly modified to reflect
the usual flow: start with conflicts, fix them, and afterwards get rid of
MERGE_HEAD, with different error messages at each stage.
Signed-off-by: NMatthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

The commit-before-pull is well accepted in the DVCS community, but is
confusing some new users. This should get them back in the right way when
the problem occurs.
Signed-off-by: NMatthieu Moy <Matthieu.Moy@imag.fr>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

These messages are nice for new users, but experienced git
users know how to manipulate the index, and these messages
waste a lot of screen real estate.
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

This message is designed to help new users understand what
has happened when refs fail to push. However, it does not
help experienced users at all, and significantly clutters
the output, frequently dwarfing the regular status table and
making it harder to see.

This patch introduces a general configuration mechanism for
optional messages, with this push message as the first
example.
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>