Making tingle portable

[stevenjm]

Hi,

I've been working on an OpenBSD driver for tingle using the new syspatch(8) utility due for release with OpenBSD 6.1.

Currently, tingle makes a few GNUish assumptions which mean that it cannot be correctly installed on a non-GNU system without patching every source file:

1. Each executable file starts with #!/bin/bash. Were this the only issue, it could be easily addressed by changing it to #!/usr/bin/env bash.
2. lib/tingle/common sets $PATH to /usr/sbin:/usr/bin:/sbin:/bin, meaning that systems which place bash in /usr/local/bin would not find it even with /usr/bin/env in the shebang.
3. Both the Makefile and the tingle source itself (when determining $TINGLE_PREFIX) assume that tingle is to be installed under /usr. This is not generally a correct assumption even on GNU systems; /usr is typically reserved for package-managed files, while a sysadmin who runs make install would expect the installation to end up under /usr/local.

The first two points can be easily resolved by removing the explicit $PATH and changing each shebang to #!/usr/bin/env bash. I do not see value in overriding whatever $PATH the sysadmin has provided.

The third is trickier, since scripts need to know how to find their libraries somehow, and bash does not provide a standard library include path. I can see three options here:

1. Provide a configure script and preprocess all of the sources during the build, which is marginally better than maintaining a separate patch for all of the sources on non-GNU platforms because it doesn't require regenerating every time the first few lines of a source file are changed.
2. Provide a configuration file in /etc which specifies where to find the system-wide tingle installation. This may be problematic because:
   • It requires parsing that configuration file in every executable, as knowing the system-wide location is necessary to load the common library routines.
   • While both GNU and OpenBSD generally place configuration in /etc for third-party software, this is not a portable assumption in general (e.g., FreeBSD uses /usr/local/etc).
3. Have each executable derive the location of its library from its own location ($0). This probably provides the best trade-off between portability and simplicity, but note that $0 may not always be a fully qualified path if the user did not invoke tingle using a fully qualified path. However, Darwin is the only system I am aware of where it is not, and tingle is unlikely to be used on Darwin systems.

I am happy to work on a solution and create a PR once I know what kind of solution might be accepted.