why does "git revert" commit even if i try to bail with ":q!"?

why does "git revert" commit even if i try to bail with ":q!"?

[Robert P. J. Day]

  never noticed this before ... when i do a regular "git commit" and
enter my "vi" edit session and change my mind, i can bail with ":q!",
regardless of what i've set up as a commit message, and i'll see:

  Aborting commit due to empty commit message.

however, i was just playing with "git revert" and, after i ran:

  $ git revert <commit SHA>

i was dumped into another vi edit session:

Revert "HTTP->HTTPS"

This reverts commit 2965b41fd84a1a76f56984ecdf6c123d1992730f.

# Please enter the commit message for your changes. Lines starting
# with '#' will be ignored, and an empty message aborts the commit.
#
# On branch master
# Your branch is up to date with 'rpjday/master'.
#
# Changes to be committed:
#       modified:   book/01-introduction/sections/installing.asc
#

  again, simulating that i changed my mind, i just typed ":q!", but
the revert went ahead, anyway. i tried again, this time completely
deleting all the lines from the commit msg (as the template
suggested), but the revert *still* completed after typing ":q!".

  it was only after deleting all the lines and using ":wq" that the
revert was cancelled:

  Aborting commit due to empty commit message.

that seems ... inconsistent. am i misunderstanding something?

rday

-- 

========================================================================
Robert P. J. Day                                 Ottawa, Ontario, CANADA
                  http://crashcourse.ca/dokuwiki

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
========================================================================

Re: why does "git revert" commit even if i try to bail with ":q!"?

[Bryan Turner]

On Tue, Mar 12, 2019 at 10:23 AM Robert P. J. Day <rpjday@crashcourse.ca> wrote:
>
>   never noticed this before ... when i do a regular "git commit" and
> enter my "vi" edit session and change my mind, i can bail with ":q!",
> regardless of what i've set up as a commit message, and i'll see:
>
>   Aborting commit due to empty commit message.
>
> however, i was just playing with "git revert" and, after i ran:
>
>   $ git revert <commit SHA>
>
>   again, simulating that i changed my mind, i just typed ":q!", but
> the revert went ahead, anyway. i tried again, this time completely
> deleting all the lines from the commit msg (as the template
> suggested), but the revert *still* completed after typing ":q!".
>
>   it was only after deleting all the lines and using ":wq" that the
> revert was cancelled:
>
>   Aborting commit due to empty commit message.
>
> that seems ... inconsistent. am i misunderstanding something?

When you're doing a fresh commit, the .git/COMMIT_MSG is "empty". It
has whitespace and comments, but no _usable_ lines. So when you :q!,
the commit is aborted because nothing Git can use as a commit message
was saved to the file and so it's still "empty".

When you use git revert, though, it writes a valid, usable message to
the file ("Revert <subject>\n\nThis reverts commit <sha>"). When you
:q!, that's still in the file. Since the file isn't empty, the commit
moves ahead.

Git doesn't actually _know_ you quit vi with :q!. All it knows is the
editor process completed with 0 exit code, and the message file isn't
"empty". If :q! made vi exit non-zero then you'd see that the commit
(or revert) got canceled because the editor failed (I don't know the
exact message off the top of my head).

An easy way to confirm this behavior would be to run your "git
revert", and, in the editor, delete all the contents, then :w and :q!.
You'll see that the revert is aborted due to an empty message. Or you
could do a normal "git commit", type a message, then :w and :q!.
You'll see that the commit still runs. So the difference between the
two is that one starts with no usable commit message, and the other
one does.

Hope this helps,
Bryan

Re: why does "git revert" commit even if i try to bail with ":q!"?

[Robert P. J. Day]

On Tue, 12 Mar 2019, Bryan Turner wrote:

> On Tue, Mar 12, 2019 at 10:23 AM Robert P. J. Day <rpjday@crashcourse.ca> wrote:
> >
> >   never noticed this before ... when i do a regular "git commit" and
> > enter my "vi" edit session and change my mind, i can bail with ":q!",
> > regardless of what i've set up as a commit message, and i'll see:
> >
> >   Aborting commit due to empty commit message.
> >
> > however, i was just playing with "git revert" and, after i ran:
> >
> >   $ git revert <commit SHA>
> >
> >   again, simulating that i changed my mind, i just typed ":q!", but
> > the revert went ahead, anyway. i tried again, this time completely
> > deleting all the lines from the commit msg (as the template
> > suggested), but the revert *still* completed after typing ":q!".
> >
> >   it was only after deleting all the lines and using ":wq" that the
> > revert was cancelled:
> >
> >   Aborting commit due to empty commit message.
> >
> > that seems ... inconsistent. am i misunderstanding something?
>
> When you're doing a fresh commit, the .git/COMMIT_MSG is "empty". It
> has whitespace and comments, but no _usable_ lines. So when you :q!,
> the commit is aborted because nothing Git can use as a commit
> message was saved to the file and so it's still "empty".

  no, if i enter the commit edit session, type some _usable_ lines,
then type ":q!", it *still* aborts the commit because of an empty
commit message. try it and tell me if it behaves differently for you.

rday

-- 

========================================================================
Robert P. J. Day                                 Ottawa, Ontario, CANADA
                  http://crashcourse.ca/dokuwiki

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
========================================================================

Re: why does "git revert" commit even if i try to bail with ":q!"?

[Kevin Daudt]

On Tue, Mar 12, 2019 at 01:22:51PM -0400, Robert P. J. Day wrote:
> 
>   never noticed this before ... when i do a regular "git commit" and
> enter my "vi" edit session and change my mind, i can bail with ":q!",
> regardless of what i've set up as a commit message, and i'll see:
> 
>   Aborting commit due to empty commit message.
> 
> however, i was just playing with "git revert" and, after i ran:
> 
>   $ git revert <commit SHA>
> 
> i was dumped into another vi edit session:
> 
> Revert "HTTP->HTTPS"
> 
> This reverts commit 2965b41fd84a1a76f56984ecdf6c123d1992730f.
> 
> # Please enter the commit message for your changes. Lines starting
> # with '#' will be ignored, and an empty message aborts the commit.
> #
> # On branch master
> # Your branch is up to date with 'rpjday/master'.
> #
> # Changes to be committed:
> #       modified:   book/01-introduction/sections/installing.asc
> #
> 
>   again, simulating that i changed my mind, i just typed ":q!", but
> the revert went ahead, anyway. i tried again, this time completely
> deleting all the lines from the commit msg (as the template
> suggested), but the revert *still* completed after typing ":q!".
> 
>   it was only after deleting all the lines and using ":wq" that the
> revert was cancelled:
> 
>   Aborting commit due to empty commit message.
> 
> that seems ... inconsistent. am i misunderstanding something?
> 
> rday

The only reason why `:q!` works just for comitting is because there is
no default message, so the final message ends up empty.

When you do things like git revert or git ocmmit --amend, there is
already a commit message, which you are then editing. When you quit
without saving, the existing message remains and git uses that.

vim has a command to let it exit with an error return code: `:cq`. This
makes git something went wrong with editing the message, causing git to
abort the commit.

Re: why does "git revert" commit even if i try to bail with ":q!"?

[Robert P. J. Day]

On Tue, 12 Mar 2019, Bryan Turner wrote:

> On Tue, Mar 12, 2019 at 10:23 AM Robert P. J. Day <rpjday@crashcourse.ca> wrote:
> >
> >   never noticed this before ... when i do a regular "git commit" and
> > enter my "vi" edit session and change my mind, i can bail with ":q!",
> > regardless of what i've set up as a commit message, and i'll see:
> >
> >   Aborting commit due to empty commit message.
> >
> > however, i was just playing with "git revert" and, after i ran:
> >
> >   $ git revert <commit SHA>
> >
> >   again, simulating that i changed my mind, i just typed ":q!", but
> > the revert went ahead, anyway. i tried again, this time completely
> > deleting all the lines from the commit msg (as the template
> > suggested), but the revert *still* completed after typing ":q!".
> >
> >   it was only after deleting all the lines and using ":wq" that the
> > revert was cancelled:
> >
> >   Aborting commit due to empty commit message.
> >
> > that seems ... inconsistent. am i misunderstanding something?

... snip ...

> When you use git revert, though, it writes a valid, usable message
> to the file ("Revert <subject>\n\nThis reverts commit <sha>"). When
> you :q!, that's still in the file. Since the file isn't empty, the
> commit moves ahead.

  again, this is also not true. as i think i mentioned in my earlier
note, if you get dropped into the revert edit session, even if you
delete all the usable commit message lines, if you type ":q!", the
revert commit still succeeds and, in fact, with all of the
revert-supplied usable lines that you just finished removing.

rday

-- 

========================================================================
Robert P. J. Day                                 Ottawa, Ontario, CANADA
                  http://crashcourse.ca/dokuwiki

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
========================================================================

Re: why does "git revert" commit even if i try to bail with ":q!"?

[Bryan Turner]

On Tue, Mar 12, 2019 at 11:01 AM Robert P. J. Day <rpjday@crashcourse.ca> wrote:
>
> On Tue, 12 Mar 2019, Bryan Turner wrote:
>
> > On Tue, Mar 12, 2019 at 10:23 AM Robert P. J. Day <rpjday@crashcourse.ca> wrote:
> > >
> > >   never noticed this before ... when i do a regular "git commit" and
> > > enter my "vi" edit session and change my mind, i can bail with ":q!",
> > > regardless of what i've set up as a commit message, and i'll see:
> > >
> > >   Aborting commit due to empty commit message.
> > >
> > > however, i was just playing with "git revert" and, after i ran:
> > >
> > >   $ git revert <commit SHA>
> > >
> > >   again, simulating that i changed my mind, i just typed ":q!", but
> > > the revert went ahead, anyway. i tried again, this time completely
> > > deleting all the lines from the commit msg (as the template
> > > suggested), but the revert *still* completed after typing ":q!".
> > >
> > >   it was only after deleting all the lines and using ":wq" that the
> > > revert was cancelled:
> > >
> > >   Aborting commit due to empty commit message.
> > >
> > > that seems ... inconsistent. am i misunderstanding something?
> >
> > When you're doing a fresh commit, the .git/COMMIT_MSG is "empty". It
> > has whitespace and comments, but no _usable_ lines. So when you :q!,
> > the commit is aborted because nothing Git can use as a commit
> > message was saved to the file and so it's still "empty".
>
>   no, if i enter the commit edit session, type some _usable_ lines,
> then type ":q!", it *still* aborts the commit because of an empty
> commit message. try it and tell me if it behaves differently for you.

Sorry, perhaps I was unclear. Even if you _type_ something, unless you
:w it's not _written_. So using :q! at that point is the same as if
you typed nothing.

But if you type something, then :w, then _as a separate command_, do
:q!, the commit _will_ be done.

Is that more clear, I hope?
Bryan

Re: why does "git revert" commit even if i try to bail with ":q!"?

[Robert P. J. Day]

On Tue, 12 Mar 2019, Kevin Daudt wrote:

... snip ...

> The only reason why `:q!` works just for comitting is because there
> is no default message, so the final message ends up empty.
>
> When you do things like git revert or git commit --amend, there is
> already a commit message, which you are then editing. When you quit
> without saving, the existing message remains and git uses that.
>
> vim has a command to let it exit with an error return code: `:cq`.
> This makes git something went wrong with editing the message,
> causing git to abort the commit.

  ah, i'm starting to get it. predictably, i think this needs to be
mentioned in a man page. :-) thanks muchly for clearing that up.

rday

-- 

========================================================================
Robert P. J. Day                                 Ottawa, Ontario, CANADA
                  http://crashcourse.ca/dokuwiki

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
========================================================================

Re: why does "git revert" commit even if i try to bail with ":q!"?

[SZEDER Gábor]

On Tue, Mar 12, 2019 at 02:14:37PM -0400, Robert P. J. Day wrote:
> On Tue, 12 Mar 2019, Bryan Turner wrote:
> 
> > On Tue, Mar 12, 2019 at 10:23 AM Robert P. J. Day <rpjday@crashcourse.ca> wrote:
> > >
> > >   never noticed this before ... when i do a regular "git commit" and
> > > enter my "vi" edit session and change my mind, i can bail with ":q!",
> > > regardless of what i've set up as a commit message, and i'll see:
> > >
> > >   Aborting commit due to empty commit message.
> > >
> > > however, i was just playing with "git revert" and, after i ran:
> > >
> > >   $ git revert <commit SHA>
> > >
> > >   again, simulating that i changed my mind, i just typed ":q!", but
> > > the revert went ahead, anyway. i tried again, this time completely
> > > deleting all the lines from the commit msg (as the template
> > > suggested), but the revert *still* completed after typing ":q!".
> > >
> > >   it was only after deleting all the lines and using ":wq" that the
> > > revert was cancelled:
> > >
> > >   Aborting commit due to empty commit message.
> > >
> > > that seems ... inconsistent. am i misunderstanding something?
> 
> ... snip ...
> 
> > When you use git revert, though, it writes a valid, usable message
> > to the file ("Revert <subject>\n\nThis reverts commit <sha>"). When
> > you :q!, that's still in the file. Since the file isn't empty, the
> > commit moves ahead.
> 
>   again, this is also not true. as i think i mentioned in my earlier
> note, if you get dropped into the revert edit session, even if you
> delete all the usable commit message lines, if you type ":q!",

If you type ':q!', then all your edits are thrown away, leaving
'.git/COMMIT_EDITMSG' intact.

> the
> revert commit still succeeds and, in fact, with all of the
> revert-supplied usable lines that you just finished removing.
> 
> rday
> 
> -- 
> 
> ========================================================================
> Robert P. J. Day                                 Ottawa, Ontario, CANADA
>                   http://crashcourse.ca/dokuwiki
> 
> Twitter:                                       http://twitter.com/rpjday
> LinkedIn:                               http://ca.linkedin.com/in/rpjday
> ========================================================================

Re: why does "git revert" commit even if i try to bail with ":q!"?

[Bryan Turner]

On Tue, Mar 12, 2019 at 11:14 AM Robert P. J. Day <rpjday@crashcourse.ca> wrote:
>
> On Tue, 12 Mar 2019, Bryan Turner wrote:
>
> > On Tue, Mar 12, 2019 at 10:23 AM Robert P. J. Day <rpjday@crashcourse.ca> wrote:
> > >
> > >   never noticed this before ... when i do a regular "git commit" and
> > > enter my "vi" edit session and change my mind, i can bail with ":q!",
> > > regardless of what i've set up as a commit message, and i'll see:
> > >
> > >   Aborting commit due to empty commit message.
> > >
> > > however, i was just playing with "git revert" and, after i ran:
> > >
> > >   $ git revert <commit SHA>
> > >
> > >   again, simulating that i changed my mind, i just typed ":q!", but
> > > the revert went ahead, anyway. i tried again, this time completely
> > > deleting all the lines from the commit msg (as the template
> > > suggested), but the revert *still* completed after typing ":q!".
> > >
> > >   it was only after deleting all the lines and using ":wq" that the
> > > revert was cancelled:
> > >
> > >   Aborting commit due to empty commit message.
> > >
> > > that seems ... inconsistent. am i misunderstanding something?
>
> ... snip ...
>
> > When you use git revert, though, it writes a valid, usable message
> > to the file ("Revert <subject>\n\nThis reverts commit <sha>"). When
> > you :q!, that's still in the file. Since the file isn't empty, the
> > commit moves ahead.
>
>   again, this is also not true. as i think i mentioned in my earlier
> note, if you get dropped into the revert edit session, even if you
> delete all the usable commit message lines, if you type ":q!", the
> revert commit still succeeds and, in fact, with all of the
> revert-supplied usable lines that you just finished removing.

Again, unless you :w and _write_ deleting the lines, the file that Git
sees still has the default message it generated. So, delete all the
lines, then :w to write that change, and then, as a separate
operation, do :q!. It won't commit the revert.

Hope this helps,
Bryan

Re: why does "git revert" commit even if i try to bail with ":q!"?

[Robert P. J. Day]

On Tue, 12 Mar 2019, Bryan Turner wrote:

> On Tue, Mar 12, 2019 at 11:01 AM Robert P. J. Day <rpjday@crashcourse.ca> wrote:
> >
> > On Tue, 12 Mar 2019, Bryan Turner wrote:
> >
> > > On Tue, Mar 12, 2019 at 10:23 AM Robert P. J. Day <rpjday@crashcourse.ca> wrote:
> > > >
> > > >   never noticed this before ... when i do a regular "git commit" and
> > > > enter my "vi" edit session and change my mind, i can bail with ":q!",
> > > > regardless of what i've set up as a commit message, and i'll see:
> > > >
> > > >   Aborting commit due to empty commit message.
> > > >
> > > > however, i was just playing with "git revert" and, after i ran:
> > > >
> > > >   $ git revert <commit SHA>
> > > >
> > > >   again, simulating that i changed my mind, i just typed ":q!", but
> > > > the revert went ahead, anyway. i tried again, this time completely
> > > > deleting all the lines from the commit msg (as the template
> > > > suggested), but the revert *still* completed after typing ":q!".
> > > >
> > > >   it was only after deleting all the lines and using ":wq" that the
> > > > revert was cancelled:
> > > >
> > > >   Aborting commit due to empty commit message.
> > > >
> > > > that seems ... inconsistent. am i misunderstanding something?
> > >
> > > When you're doing a fresh commit, the .git/COMMIT_MSG is "empty". It
> > > has whitespace and comments, but no _usable_ lines. So when you :q!,
> > > the commit is aborted because nothing Git can use as a commit
> > > message was saved to the file and so it's still "empty".
> >
> >   no, if i enter the commit edit session, type some _usable_ lines,
> > then type ":q!", it *still* aborts the commit because of an empty
> > commit message. try it and tell me if it behaves differently for you.
>
> Sorry, perhaps I was unclear. Even if you _type_ something, unless
> you :w it's not _written_. So using :q! at that point is the same as
> if you typed nothing.
>
> But if you type something, then :w, then _as a separate command_, do
> :q!, the commit _will_ be done.
>
> Is that more clear, I hope?
> Bryan

  yes, i appreciate all the clarification.

rday

-- 

========================================================================
Robert P. J. Day                                 Ottawa, Ontario, CANADA
                  http://crashcourse.ca/dokuwiki

Twitter:                                       http://twitter.com/rpjday
LinkedIn:                               http://ca.linkedin.com/in/rpjday
========================================================================

Re: why does "git revert" commit even if i try to bail with ":q!"?

[Elijah Newren]

On Tue, Mar 12, 2019 at 11:21 AM Robert P. J. Day <rpjday@crashcourse.ca> wrote:
>
> On Tue, 12 Mar 2019, Kevin Daudt wrote:
>
> ... snip ...
>
> > The only reason why `:q!` works just for comitting is because there
> > is no default message, so the final message ends up empty.
> >
> > When you do things like git revert or git commit --amend, there is
> > already a commit message, which you are then editing. When you quit
> > without saving, the existing message remains and git uses that.
> >
> > vim has a command to let it exit with an error return code: `:cq`.
> > This makes git something went wrong with editing the message,
> > causing git to abort the commit.
>
>   ah, i'm starting to get it. predictably, i think this needs to be
> mentioned in a man page. :-) thanks muchly for clearing that up.

If you do fix up some manpage, note that this affects e.g. commit
--amend too as pointed out by Kevin (and maybe also the 'reword'
option of git-rebase?) -- anything that starts with .git/COMMIT_MSG
being non-empty.