Re: Is there a way to have a local version of a header file?

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

On Sat, Mar 18, 2017 at 3:58 PM, David Lang <david@lang.hm> wrote:
> On Sat, 18 Mar 2017, Ævar Arnfjörð Bjarmason wrote:
>
>> On Sat, Mar 18, 2017 at 3:29 PM, David Lang <david@lang.hm> wrote:
>>>
>>> for an embedded project built inside the Arduino IDE, (alternate firmware
>>> for a home automation project) there is a need to set a number of
>>> parameters
>>> that we really don't want in the main repo (wifi network IDs/passwords)
>>>
>>> right now, we have these things set as #defines in a header file.
>>>
>>> We need to distribute a base version of this file for new people to get
>>> started.
>>>
>>> Is there any way to have git define a file in such a way that if it
>>> doesn't
>>> exist in the worktree it gets populated, but if it does exist it doesn't
>>> get
>>> overwritten? (as I type this, I'm thinking a trigger may work, but we
>>> need
>>> it to work on Linux, Windows and OSX)
>>>
>>> Any thoughts on a sane way to handle this situation?
>>
>>
>> There's no sane way to do what you're describing without renaming the
>> file.
>>
>> But the sanest way to do this is to have a config.h.example
>>
>> Then you have "/config.h" in the .gitignore file.
>>
>> And you tell the users to copy the *.example file to *.h, and your
>> program then includes the *.h file.
>>
>> If you wanted to provide defaults you could just #include the
>> config.h.example first, so #defines in the *.h file would clobber
>> those in the *.example.
>
>
> That's what we currently have (user_config.h and user_config_override.h)
>
> I was hoping to not have the situation where downloading and trying to
> compile will complain about a missing include file (if the users don't copy
> user_config_override_example.h to user_config_override.h) while letting us
> do a .gitignore on user_config_override.h
>
> for many people using this project, this is the first time they have ever
> compiled anything, and we have the typical set of people not reading
> instructions :-/
>
> Darn, I was hoping that the scenario of needing to have a config file
> provided in the repo, while not overwriting local changes to it was common
> enough that there were some tricks available. This is a little harder as the
> running code doesn't have a filesystem so we are limited to what we can do
> in the compiler and git (no makefile even, the Arduino folks consider that
> too complicated, it just slurps up all .ino files in a directory and
> compiles them)

There might be some way I haven't thought of, in particular maybe you
can use gitattributes to define a custom diff/merge driver that always
reports no changes, or some ways to (ab)use the index to make git
ignore any changes to the file.