[ANNOUNCE] EasyGit (eg) 0.97

[ANNOUNCE] EasyGit (eg) 0.97

[Elijah Newren]

=== What is Easy Git? ===

Easy Git (eg) is an alternative frontend for git, specifically designed for
former cvs and svn users in order to provide a lower learning curve and
prevent common user errors.  Since eg largely looks and feels like core
git, eg can also serve as a training tool to teach users git (see below for
similarities and how to display git commands that eg uses).  There is a
detailed side-by-side comparison of svn and eg to help svn users make the
switch[1].  eg is trivial to install and try out: simply download a single
file and stick it in your PATH[2].

=== How different is eg from git? ===

eg is nearly backward-compatible to the core git porcelain, meaning that
you can take any git command, replace "git" with "eg" and run it[3]; I
believe that any behavioral differences between eg and git can be
discovered naturally and innocuously by an existing git user during normal
use of eg.  Also, you can switch back and forth between git and eg commands
in the same project.  Finally, eg is also somewhat forward-compatible with
the git porcelain, by which I mean that new flags to git commands are often
supported automatically in eg even if no modifications are made to eg.

=== If eg is so similar, what is the difference between eg and git? ===

Differences between eg and git[4] basically boil down to:
* eg has a replacement help system that is tutorial oriented for new users
  (these help pages do refer to the git manpages, for more in-depth details)
* eg does extra error checking to avoid some common gotchas
* eg changes some defaults, particularly where git defaults cause
  significant confusion and/or common gotchas for users
* eg has some (occasionally gratuitous) new svn-compatibility subcommands
  (cat, resolved, switch, update)

=== How far along is eg? ===

eg is essentially complete and has been for a while; I've used it daily
since last February, and there are multiple other users who do as well.
I've even benefitted from having some users who barely grasp the basics of
CVS who have tried eg and provided feedback ("[utterly broken workflow] is
what I do in CVS!  To figure out how to do that in eg I had to go _read_
some of the help pages -- why can't you make it easy?")

eg has just one major bug left that I know of[5]; otherwise it's
essentially 1.0.  eg requires fairly minimal maintainance -- most new
capabilities in git are automatically accessible through eg due to eg's
design of passing arguments on to git after optionally massaging them or
doing extra checks.  In fact, this design also means eg users can benefit
from documentation meant for core git, and that eg users should often be
able to get help from git users without git users really needing to learn a
different UI.  On the downside, this design also means that (a) eg feels
like an incomplete solution ("why does this message suggest running 'git
rebase --continue' when I'm using eg rather than git?"), and (b) eg's
interface is not simplified as much as it could be by focusing on a
specific use-case (e.g. centralized development) or providing a more
orthogonal UI[6].  It does, however, ease transition between the two tools
and potentially provide a testbed for ideas that could be adopted by git
more easily.

=== What's the path forward? ===

I have no idea.  It turns out that eg allowed me to overcome the concerns
of others at work that "git was too difficult to use", and was an important
part of convincing them to switch to git instead of svn (we're stuck with
CVS right now but are working on switching).  So eg won't die, unless git
itself adopts enough of the improvements in eg.  And really, some stuff
from eg may just not belong in git, so it may make sense to have an
independent script indefinitely (though it could certainly be made much
smaller).

What makes sense to the community?  Some possibilities:
* Keep working on eg completely independently
* Propose eg (and perhaps eg-completion.bash) for contrib
* Start a series of discussions on individual changes from eg and see which
  ones the community thinks make sense in git
* Have me stop being lazy and create patches for git as a basis of
  discussion
* Let the crickets chirp (i.e. just ignore this weird Easy Git guy)
* Some combination of the above, or maybe something else entirely?



Elijah


[1] http://www.gnome.org/~newren/eg/git-for-svn-users.html
[2] http://www.gnome.org/~newren/eg/download, or
[3] If you're curious if/how/when eg changes arguments before passing them
to git, you can run "eg --debug ARGS..." to see the git commands eg is
running.  If you just want to see the git commands that eg would run
without them also being executed, you can run "eg --translate ARGS..."
[4] For detailed differences, see
http://www.gnome.org/~newren/eg/git-eg-differences.html
[5] The bug I can only occasionally trigger and which I don't know the
cause of yet: when exiting from eg log the terminal settings sometimes
are messed up (with echo off and such), requiring a "reset" to get the
terminal back to normal.
[6] http://marc.info/?l=git&m=122071366316713&w=1

Re: [ANNOUNCE] EasyGit (eg) 0.97

[Mike Ralphson]

2009/1/30 Elijah Newren <newren@gmail.com>:
> [5] The bug I can only occasionally trigger and which I don't know the
> cause of yet: when exiting from eg log the terminal settings sometimes
> are messed up (with echo off and such), requiring a "reset" to get the
> terminal back to normal.

Are you sure that isn't this bug in git.git ?

pager: do wait_for_pager on signal death
http://article.gmane.org/gmane.comp.version-control.git/106728

Mike

Re: [ANNOUNCE] EasyGit (eg) 0.97

[Elijah Newren]

On Fri, Jan 30, 2009 at 9:59 AM, Mike Ralphson <mike.ralphson@gmail.com> wrote:
> 2009/1/30 Elijah Newren <newren@gmail.com>:
>> [5] The bug I can only occasionally trigger and which I don't know the
>> cause of yet: when exiting from eg log the terminal settings sometimes
>> are messed up (with echo off and such), requiring a "reset" to get the
>> terminal back to normal.
>
> Are you sure that isn't this bug in git.git ?
>
> pager: do wait_for_pager on signal death
> http://article.gmane.org/gmane.comp.version-control.git/106728

Interesting.  I just went and tried out next (git version
1.6.1.2.418.gd79e6), which I believe has this patch...and after a
while I was still able to duplicate the eg bug on one of my
machines[1].  So it doesn't seem to be that particular issue, at
least.

Thanks for the pointer.

Elijah


[1] Output of stty after I trigger the eg/git bug:
speed 38400 baud; line=0;
lnext = <undef>; min = 1; time = 0;
-icrnl
-icanon -echo

Re: [ANNOUNCE] EasyGit (eg) 0.97

[Jeff King]

On Fri, Jan 30, 2009 at 11:35:50AM -0700, Elijah Newren wrote:

> > 2009/1/30 Elijah Newren <newren@gmail.com>:
> >> [5] The bug I can only occasionally trigger and which I don't know the
> >> cause of yet: when exiting from eg log the terminal settings sometimes
> >> are messed up (with echo off and such), requiring a "reset" to get the
> >> terminal back to normal.
> >
> > Are you sure that isn't this bug in git.git ?
> >
> > pager: do wait_for_pager on signal death
> > http://article.gmane.org/gmane.comp.version-control.git/106728
> 
> Interesting.  I just went and tried out next (git version
> 1.6.1.2.418.gd79e6), which I believe has this patch...and after a
> while I was still able to duplicate the eg bug on one of my
> machines[1].  So it doesn't seem to be that particular issue, at
> least.

There is also a related set of fixes for spawning externals via fork,
which fixes a bug with the pager not getting cleaned up. But it looks
like it is also in the version you tested.

Can you give a more complete recipe for reproducing? Since I was just
touching this area in git, I want to make sure it isn't a git bug you
are triggering. :)

As an aside, I found some related weirdness. In my git repo, if I do
this:

  $ git checkout next
  $ eg log -p

I get log output, but the diff is not colorized (and I have color.diff
set to "auto" in my ~/.gitconfig). But if I detach my HEAD and show the
log:

  $ git checkout next^0
  $ eg log -p

then I _do_ get color in the patch. I also get this error:

  Use of uninitialized value $branch in concatenation (.) or string at
  /home/peff/eg line 2854.
  eg: command (git rev-parse refs/heads/) failed
  eg: received signal 13

The error is easy to explain. The offending code is:

    my $branch = RepoUtil::current_branch();
    my ($ret, $revision) =
      ExecUtil::execute_captured("git rev-parse refs/heads/$branch");

So it is clear that you just need to handle the case of there being no
current branch. But the color thing is certainly exotic. :)

-Peff

Re: [ANNOUNCE] EasyGit (eg) 0.97

[Jeff King]

On Fri, Jan 30, 2009 at 02:47:27PM -0500, Jeff King wrote:

> There is also a related set of fixes for spawning externals via fork,
> which fixes a bug with the pager not getting cleaned up. But it looks
> like it is also in the version you tested.
> 
> Can you give a more complete recipe for reproducing? Since I was just
> touching this area in git, I want to make sure it isn't a git bug you
> are triggering. :)

Ah, OK. I just peeked through the 'eg' source. It looks like you may
have replicated the same bug that I just fixed in git. :)

You  want to make sure that "eg" is the last process to die (i.e.,
_after_ the pager). Otherwise after it dies, less has trouble reading
from the terminal (I don't know for sure, but I assume this has to do
with the shell making "eg" the process group leader and magic about
process groups and controlling terminals).

I think perl may even do the wait() for you under ordinary
circumstances. But, for example, if I kill "eg" with a signal (say, by
hitting ^C), then it will die but the pager will live on. In git, we
catch the signal and wait() before dying.

So I don't know for sure that is your problem (it really depends on how
much magic perl is doing behind the scenes with wait()ing on children,
and I don't recall the exact details of that). But it is something to
look into.

I don't think it's a git problem, though. "eg log" doesn't spawn a git
pager, since you pipe the output into eg. The paging is all your local
"less" invocation.

-Peff

Re: [ANNOUNCE] EasyGit (eg) 0.97

[Elijah Newren]

On Fri, Jan 30, 2009 at 12:47 PM, Jeff King <peff@peff.net> wrote:
> As an aside, I found some related weirdness. In my git repo, if I do
> this:
>
>  $ git checkout next
>  $ eg log -p
>
> I get log output, but the diff is not colorized (and I have color.diff
> set to "auto" in my ~/.gitconfig). But if I detach my HEAD and show the
> log:
>
>  $ git checkout next^0
>  $ eg log -p
>
> then I _do_ get color in the patch. I also get this error:

Hmm, I had never turned color on before; I guess other eg users hadn't
either.  Anyway, the difference can be explained pretty easily:  eg
log tries to provide user-meaningful names for how commits relate to
the active branch (like git-name-rev but implemented internally in eg
to allow the common case to be fast); if there is no active branch
there's no special naming to do so I simply run git log without
reading and modifying its output.

Essentially, the difference in coloring here is much like the
difference you see between

$ git log
$ git log | less

Whenever I try to load the output in perl, git won't show the
colorization.  I guess I could manually add it when I am printing the
information, but it'd be nicer to just have git do the colorization
despite the fact that its output is not a tty.  Is there an easy way
to do that (without mucking with the user's config file)?

(It looks like eg status is also affected, for similar reasons.)

>  Use of uninitialized value $branch in concatenation (.) or string at
>  /home/peff/eg line 2854.
>  eg: command (git rev-parse refs/heads/) failed
>  eg: received signal 13
>
> The error is easy to explain. The offending code is:
>
>    my $branch = RepoUtil::current_branch();
>    my ($ret, $revision) =
>      ExecUtil::execute_captured("git rev-parse refs/heads/$branch");

Indeed, the latter two lines should have been after the if (!$branch) check.


Thanks,
Elijah

Re: [ANNOUNCE] EasyGit (eg) 0.97

[Elijah Newren]

On Fri, Jan 30, 2009 at 1:03 PM, Jeff King <peff@peff.net> wrote:
> Ah, OK. I just peeked through the 'eg' source. It looks like you may
> have replicated the same bug that I just fixed in git. :)
>
> You  want to make sure that "eg" is the last process to die (i.e.,
> _after_ the pager). Otherwise after it dies, less has trouble reading
> from the terminal (I don't know for sure, but I assume this has to do
> with the shell making "eg" the process group leader and magic about
> process groups and controlling terminals).
>
> I think perl may even do the wait() for you under ordinary
> circumstances. But, for example, if I kill "eg" with a signal (say, by
> hitting ^C), then it will die but the pager will live on. In git, we
> catch the signal and wait() before dying.
>
> So I don't know for sure that is your problem (it really depends on how
> much magic perl is doing behind the scenes with wait()ing on children,
> and I don't recall the exact details of that). But it is something to
> look into.

Thanks for the tips; I'll try to take a look and see what I can figure out.


Elijah

Re: [ANNOUNCE] EasyGit (eg) 0.97

[Jeff King]

On Fri, Jan 30, 2009 at 01:21:00PM -0700, Elijah Newren wrote:

> Whenever I try to load the output in perl, git won't show the
> colorization.  I guess I could manually add it when I am printing the
> information, but it'd be nicer to just have git do the colorization
> despite the fact that its output is not a tty.  Is there an easy way
> to do that (without mucking with the user's config file)?
> 
> (It looks like eg status is also affected, for similar reasons.)

If you pass --color on the command line, it is equivalent to "color =
always" (whereas the default is "auto", which turns it on only if output
is to a tty).

So you would have to read color.diff yourself and then decide whether to
add --color.

Note that in general you are playing things a bit risky with these sorts
of outputs. You are calling porcelain (like log and status) and piping
it into your program. There's no guarantee that user config might not be
affecting the results of those programs.

But I think that is sort of the nature of "eg": to be a thin wrapper
around git. So maybe it is OK for your use.

-Peff

Re: [ANNOUNCE] EasyGit (eg) 0.97

[Elijah Newren]

On Fri, Jan 30, 2009 at 1:29 PM, Jeff King <peff@peff.net> wrote:
> If you pass --color on the command line, it is equivalent to "color =
> always" (whereas the default is "auto", which turns it on only if output
> is to a tty).
>
> So you would have to read color.diff yourself and then decide whether to
> add --color.

It looks like I can also set the environment variable GIT_PAGER_IN_USE
to achieve the same effects (and I don't even need to do so for most
commands, such as diff, just those whose output I'm parsing and
possibly tweaking).

> Note that in general you are playing things a bit risky with these sorts
> of outputs. You are calling porcelain (like log and status) and piping
> it into your program. There's no guarantee that user config might not be
> affecting the results of those programs.
>
> But I think that is sort of the nature of "eg": to be a thin wrapper
> around git. So maybe it is OK for your use.

Right, I considered switching eg to use git plumbing commands to
insulate from issues like this, but the problem is that if git output
changes then the eg output really should change too (or else I should
have a very specific reason for not changing it).  This almost
certainly means that I'll have to bump the minimum git version to be
used with eg at some point, but that seemed the most reasonable path
for eg.

Re: [ANNOUNCE] EasyGit (eg) 0.97

[Jeff King]

On Fri, Jan 30, 2009 at 03:55:28PM -0700, Elijah Newren wrote:

> > So you would have to read color.diff yourself and then decide whether to
> > add --color.
> 
> It looks like I can also set the environment variable GIT_PAGER_IN_USE
> to achieve the same effects (and I don't even need to do so for most
> commands, such as diff, just those whose output I'm parsing and
> possibly tweaking).

Ah, right. I forgot about that. Yes, setting GIT_PAGER_IN_USE should
work, I think.

-Peff