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    config: add ctx arg to config_fn_t · a4e7e317
    Glen Choo authored and Junio C Hamano's avatar Junio C Hamano committed
    
    
    Add a new "const struct config_context *ctx" arg to config_fn_t to hold
    additional information about the config iteration operation.
    config_context has a "struct key_value_info kvi" member that holds
    metadata about the config source being read (e.g. what kind of config
    source it is, the filename, etc). In this series, we're only interested
    in .kvi, so we could have just used "struct key_value_info" as an arg,
    but config_context makes it possible to add/adjust members in the future
    without changing the config_fn_t signature. We could also consider other
    ways of organizing the args (e.g. moving the config name and value into
    config_context or key_value_info), but in my experiments, the
    incremental benefit doesn't justify the added complexity (e.g. a
    config_fn_t will sometimes invoke another config_fn_t but with a
    different config value).
    
    In subsequent commits, the .kvi member will replace the global "struct
    config_reader" in config.c, making config iteration a global-free
    operation. It requires much more work for the machinery to provide
    meaningful values of .kvi, so for now, merely change the signature and
    call sites, pass NULL as a placeholder value, and don't rely on the arg
    in any meaningful way.
    
    Most of the changes are performed by
    contrib/coccinelle/config_fn_ctx.pending.cocci, which, for every
    config_fn_t:
    
    - Modifies the signature to accept "const struct config_context *ctx"
    - Passes "ctx" to any inner config_fn_t, if needed
    - Adds UNUSED attributes to "ctx", if needed
    
    Most config_fn_t instances are easily identified by seeing if they are
    called by the various config functions. Most of the remaining ones are
    manually named in the .cocci patch. Manual cleanups are still needed,
    but the majority of it is trivial; it's either adjusting config_fn_t
    that the .cocci patch didn't catch, or adding forward declarations of
    "struct config_context ctx" to make the signatures make sense.
    
    The non-trivial changes are in cases where we are invoking a config_fn_t
    outside of config machinery, and we now need to decide what value of
    "ctx" to pass. These cases are:
    
    - trace2/tr2_cfg.c:tr2_cfg_set_fl()
    
      This is indirectly called by git_config_set() so that the trace2
      machinery can notice the new config values and update its settings
      using the tr2 config parsing function, i.e. tr2_cfg_cb().
    
    - builtin/checkout.c:checkout_main()
    
      This calls git_xmerge_config() as a shorthand for parsing a CLI arg.
      This might be worth refactoring away in the future, since
      git_xmerge_config() can call git_default_config(), which can do much
      more than just parsing.
    
    Handle them by creating a KVI_INIT macro that initializes "struct
    key_value_info" to a reasonable default, and use that to construct the
    "ctx" arg.
    
    Signed-off-by: default avatarGlen Choo <chooglen@google.com>
    Signed-off-by: default avatarJunio C Hamano <gitster@pobox.com>
    a4e7e317