Re: [PATCH] Allow overriding the home directory via the HOME variable

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

Hi Corinna,

On Wed, 21 Oct 2015, Corinna Vinschen wrote:

> On Sep 16 15:06, Johannes Schindelin wrote:
> > 	* uinfo.cc (cygheap_pwdgrp::get_home): Offer an option in
> > 	nsswitch.conf that let's the environment variable HOME (or
> > 	HOMEDRIVE & HOMEPATH, or USERPROFILE) define the home
> > 	directory.
> > 
> > 	* ntsec.xml: Document the `env` schema.
> > 
> > Detailed comments:
> > 
> > In the context of Git for Windows, it is a well-established technique
> > to let the `$HOME` variable define where the current user's home
> > directory is, falling back to `$HOMEDRIVE$HOMEPATH` and `$USERPROFILE`.
> > 
> > The idea is that we want to share user-specific settings between
> > programs, whether they be Cygwin, MSys2 or not.  Unfortunately, we
> > cannot blindly activate the "db_home: windows" setting because in some
> > setups, the user's home directory is set to a hidden directory via an
> > UNC path (\\share\some\hidden\folder$) -- something many programs
> > cannot handle correctly.
> 
> -v, please.  Which applications can't handle that?  Why do we have to
> care?

Oh, the first one that comes to mind is `cmd.exe`. You cannot start
`cmd.exe` with a UNC working directory without getting complaints.

> > The established technique is to allow setting the user's home directory
> > via the environment variables mentioned above.  This has the additional
> > advantage that it is much faster than querying the Windows user database.
> 
> But it's wrong.  We discussed this a couple of times on the Cygwin ML.
> The underlying functionality generically implements the passwd entries.
> Your "env" setting will return the same $HOME setting in the pw_dir
> field for every user account.

No, it will not, because most users are not administrators. So they can
only set environment variables for themselves.

In most cases, `HOME` will not even be defined, but `HOMEDRIVE` and
`HOMEPATH` will, and they will be correct.

> All user accounts will have the same home dir as your current user.  And
> the value is unreliable, too.  If another user logs in, all accounts
> will have another $HOME, the one from the now logged in user.  This is
> so wrong and potentially dangerous that I don't think this belongs into
> Cygwin, sorry.

I ask you to reconsider. I am not trying to make this the default. And I
*need* a way to heed the `HOME` variable set by the user. For
backwards-compatibility with Git for Windows 1.x, where users frequently
adjusted the `HOME` variable to fix problems with MSys not handling their
home directory properly.

The patch itself is so simple that it cannot possibly cause a maintenance
burden, and by offering this feature as opt-in, users who are in need of
that feature can easily use it -- in Cygwin, MSys2, and yes, in Git for
Windows.

It would bring a major benefit to us.

Ciao,
Johannes