It turns out that trying to use -- to "escape" the - filename alias is not conventional (as i initially believed it to be). That aspect of this change accounts for the vast majority of the code, so a separate branch will be created with a much-simplified form which only provides (more or less) POSIX-conventional handling of --.

Management Summary

The double-dash-flag branch aims to add support for the conventional interpretation of a -- flag: all arguments after the first instance of -- are to be treated as non-flag arguments (e.g. file/wiki/branch/whatever names).

This feature request is from: https://fossil-scm.org/forum/forumpost/64acc6b653

The implementation is not 100% compliant with POSIX/Unix conventions because it cannot be without Breaking Stuff, but it "should" be close enough to be useful/conventional for the contexts where using -- makes sense in Fossil. For example, uv add treats a filename of - as stdin by default (and has valid use cases enabled by that), and -- could be used to make uv add treat - as a filename (that's the original use case for which conventional -- support was proposed).

Compatibility vs. Historical Behaviour

Fossil's historical handling of -- is really weird: the first time find_option() encounters --, it removes that flag and stops processing arguments. Subsequent calls to find_option() then never see -- and thus treat all arguments as potential flags (even those after the prior position of --). Since that behaviour was never useful, and potentially confusing, it is unexpected that the changes made in this branch will break any historical usage of the CLI commands.

For example:

fossil foo -- -a -b -c

The current (trunk, as of this writing) interpretation of -a -b -c, because of the "one-time-swallowing" of --, depends on what order those flags are checked for via find_option(). It seems highly unlikely that anyone could have reliably depended on that, and therefore seems unlikely that this change will break anyone's scripts.

Commands which accept a filename as the value of a flag are unaffected by these changes, provided the flag comes before --:

fossil foo -R - -- -a -b -c

Would (both before and after this change) treat - as a repository file name, but this change will cause the subsequent -a -b -c flags to be interpreted as non-flags (it's then up to the foo command to deal with them).

This Implementation's Behaviour

1. find_option() and its variants always stop looking for flags when they encounter --.
2. verify_all_options() triggers a fatal error if -- is found in the argument list.
3. verify_all_options2() consumes the first instance of -- and records the g.argv index where -- was found in g.argDashDashIndex, so that commands which need to can determine whether, e.g., an argument of - should be treated as an alias for stdin/stdout or as a literal filename (the latter only applies if -- precedes the - argument). The utility function get_dash_filename_arg() makes that particular use case trivial to implement.

It seems, after having migrated many of the commands, that it would be harmless/risk-free, and probably desirable, to eliminate verify_all_options2() and have verify_all_options() adopt that function's behaviour. That would make a stray -- flag at the end of a command a harmless no-op for commands which don't/can't make any special use of it, whereas it would "hide" flags (treating them as non-flags) if it's used before the end of such a command (indeed, that's its whole intention).

List of commands/subcommands extended to support --

(Alphabetized by command/subcommand name.)

• 3-way-merge
• add
• annotate
• artifact
• branch new: you might recall Johnny Cash's song The Branch Named --Sue.
• cat
• changes/status
• clean
• clone
• commit
• diff/gdiff
• extras
• finfo
• grep
• ls
• mv/rename
• new/init
• open
• revert
• rm/delete/forget
• stash save | snapshot
• sqlar
• tarball
• uv add | cat | edit | export | rm (noting that export has one pathological(?) corner case which we can't 100% accommodate: double-dashing the UVFILE name without applying double-dash to the output file name).
• wiki commit | create | export
• zip

The Obligatory Exceptions

• diff -tk and stash diff -tk: diff_tk() does not use verify_all_options(), so it has historically silently ignored unknown flags. To avoid breaking existing user behaviour, it was not modified. Ideally it should be updated to call verify_all_options2().
• stash gdiff|show|gshow|cat|gcat do not currently call verify_all_options(), but probably should.
• search does not use verify_all_options(), instead treating all unconsumed flag arguments as a search pattern. It can easily be made to treat -- as the other commands, but doing so may break existing expectations, so that command was left unmodified.
• tag does not use verify_all_options(), instead using strictly positional arguments, thus it supports tags with leading dashes as-is.