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From: Heba Waly <heba.waly@gmail.com>
To: Emily Shaffer <emilyshaffer@google.com>
Cc: Heba Waly via GitGitGadget <gitgitgadget@gmail.com>,
	git@vger.kernel.org, Junio C Hamano <gitster@pobox.com>
Subject: Re: [PATCH 1/1] config: add documentation to config.h
Date: Sun, 20 Oct 2019 21:35:17 +1300	[thread overview]
Message-ID: <CACg5j26DuAUm9WR9-4awF7BeGCy81d5kMhhcsePyp3Kxh2DTGg@mail.gmail.com> (raw)
In-Reply-To: <20191018225155.GA9323@google.com>

On Sat, Oct 19, 2019 at 11:52 AM Emily Shaffer <emilyshaffer@google.com> wrote:
>
> On Fri, Oct 18, 2019 at 12:06:59AM +0000, Heba Waly via GitGitGadget wrote:
> > From: Heba Waly <heba.waly@gmail.com>
>
> Hi Heba,
>
> Thanks for the patch!
>
> I'd like to highlight to the community that this is an Outreachy
> applicant and microproject. Heba, when you send the next version, I
> think you can add [Outreachy] manually to the PR subject line - that
> should draw the attention of those in the community who are invested in
> helping Outreachy applicants.
Good idea! I wanted to add it to the email subject but as I decided to
use gitgadget
I had no control over the subject.
> >
> > This commit is copying and summarizing the documentation from
> > documentation/technical/api-config.txt to comments in config.h
>
> I think in the GitGitGadget PR you've got some great comments from Dscho
> about how to format your commit message; please take a look at those and
> feel free to reach out to me if you're still not sure what's missing or
> not.
Will do.
> > Signed-off-by: Heba Waly <heba.waly@gmail.com>
>
> One thing I miss in this change is the removal of the contents of
> Documentation/technical/api-config.txt (or maybe the removal of the file
> itself). I'd prefer to see at least for api-config.txt to say something
> like "Please refer to comments in 'config.h'"; or, more drastically, for
> api-config.txt to be removed entirely.
>
> Having both pieces of documentation standing independently means that
> someone who's trying to add new information about the config API won't
> know where to add it; eventually they'll add something to config.h but
> not api-config.txt, or vice versa, and the two documents will go out of
> sync. So we want to move the documentation, rather than copy it.
That makes sense, thanks for the explanation.
I wasn't sure if it should be removed or not so I decided to leave it
until I'm asked otherwise.
So I assume api-config.html will be removed too?
> Plus, having the removed doc as part of this change means I can more
> easily look at where the lines of content are coming from and see if you
> made any significant changes from the old contents of api-config.txt.
> Having a smaller amount of change to review means your review will be
> quicker - I don't feel as strong a need to check the grammar, spelling,
> etc, because that text has already been reviewed before, and can just
> make sure that the placement of each piece of documentation makes sense.
yes!
>
> > ---
> >  config.h | 327 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 327 insertions(+)
> >
> > diff --git a/config.h b/config.h
> > index f0ed464004..fa999a2ba0 100644
> > --- a/config.h
> > +++ b/config.h
> > @@ -4,6 +4,40 @@
> >  #include "hashmap.h"
> >  #include "string-list.h"
> >
> > +
> > +/**
> > + * The config API gives callers a way to access Git configuration files
> > + * (and files which have the same syntax). See linkgit:git-config[1] for a
> > + * discussion of the config file syntax.
> > + *
> > + * General Usage
> > + * -------------
> > + *
> > + * Config files are parsed linearly, and each variable found is passed to a
> > + * caller-provided callback function. The callback function is responsible
> > + * for any actions to be taken on the config option, and is free to ignore
> > + * some options. It is not uncommon for the configuration to be parsed
> > + * several times during the run of a Git program, with different callbacks
> > + * picking out different variables useful to themselves.
> > + *
> > + * A config callback function takes three parameters:
> > + *
> > + * - the name of the parsed variable. This is in canonical "flat" form: the
> > + *   section, subsection, and variable segments will be separated by dots,
> > + *   and the section and variable segments will be all lowercase. E.g.,
> > + *   `core.ignorecase`, `diff.SomeType.textconv`.
> > + *
> > + * - the value of the found variable, as a string. If the variable had no
> > + *   value specified, the value will be NULL (typically this means it
> > + *   should be interpreted as boolean true).
> > + *
> > + * - a void pointer passed in by the caller of the config API; this can
> > + *   contain callback-specific data
> > + *
> > + * A config callback should return 0 for success, or -1 if the variable
> > + * could not be parsed properly.
> > + */
> > +
> >  struct object_id;
> >
> >  /* git_config_parse_key() returns these negated: */
> > @@ -73,6 +107,11 @@ struct config_options {
> >
> >  typedef int (*config_fn_t)(const char *, const char *, void *);
> >  int git_default_config(const char *, const char *, void *);
> > +
> > +/**
> > + * Read a specific file in git-config format.
> > + * This function takes the same callback and data parameters as `git_config`.
> > + */
> >  int git_config_from_file(config_fn_t fn, const char *, void *);
> >  int git_config_from_file_with_options(config_fn_t fn, const char *,
> >                                     void *,
> > @@ -88,33 +127,152 @@ void git_config_push_parameter(const char *text);
> >  int git_config_from_parameters(config_fn_t fn, void *data);
> >  void read_early_config(config_fn_t cb, void *data);
> >  void read_very_early_config(config_fn_t cb, void *data);
> > +
> > +/**
> > + * Most programs will simply want to look up variables in all config files
> > + * that Git knows about, using the normal precedence rules. To do this,
> > + * call `git_config` with a callback function and void data pointer.
> > + *
> > + * `git_config` will read all config sources in order of increasing
> > + * priority. Thus a callback should typically overwrite previously-seen
> > + * entries with new ones (e.g., if both the user-wide `~/.gitconfig` and
> > + * repo-specific `.git/config` contain `color.ui`, the config machinery
> > + * will first feed the user-wide one to the callback, and then the
> > + * repo-specific one; by overwriting, the higher-priority repo-specific
> > + * value is left at the end).
> > + */
> >  void git_config(config_fn_t fn, void *);
> > +
> > +/**
> > + * Lets the caller examine config while adjusting some of the default
> > + * behavior of `git_config`. It should almost never be used by "regular"
> > + * Git code that is looking up configuration variables.
> > + * It is intended for advanced callers like `git-config`, which are
> > + * intentionally tweaking the normal config-lookup process.
> > + * It takes two extra parameters:
> > + *
> > + * `config_source`::
>
> I think the wonky trailing "::" is for generating manpages/HTML out of
> the asciidoc from the original api-config.txt. I expect it's OK to
> remove them throughout this change and format this in a way that makes more
> sense for comments which won't be converted into anything else.
Good catch! thanks, will change that.

> > + * If this parameter is non-NULL, it specifies the source to parse for
> > + * configuration, rather than looking in the usual files. See `struct
> > + * git_config_source` in `config.h` for details. Regular `git_config` defaults
> > + * to `NULL`.
> > + *
> > + * `opts`::
> > + * Specify options to adjust the behavior of parsing config files. See `struct
> > + * config_options` in `config.h` for details. As an example: regular `git_config`
> > + * sets `opts.respect_includes` to `1` by default.
> > + */
> >  int config_with_options(config_fn_t fn, void *,
> >                       struct git_config_source *config_source,
> >                       const struct config_options *opts);
> > +
> > +/**
> > + * Value Parsing Helpers
> > + * ---------------------
>
> It may not make sense to have the header here in the middle of the doc.
>
> I wonder whether we need the headers at all anymore; or, whether it
> makes more sense to put this header in the long comment at the top with
> just the list of function names (so someone knows where to look), and
> leave the per-function explanations inline with the function they
> describe?
I see your point Emily, but in the CodingGuidelines file it was
advised to refer to strbuf.h
as a model for documentation, I noticed that strbuf.h used headers
this way so I decided
to replicate that.
> > + *
> > + * To aid in parsing string values, the config API provides callbacks with
> > + * a number of helper functions
>
> In the copy paste, this lost some ending punctuation. I'd advocate
> ending this with ":" to indicate "we are about to give the list of those
> functions". Although, I wonder whether it makes more sense to rephrase
> this into something like "The following helper functions aid in parsing
> string values:"? Not sure.
I like that. will rephrase it.
> > + */
> > +
> >  int git_parse_ssize_t(const char *, ssize_t *);
> >  int git_parse_ulong(const char *, unsigned long *);
> > +
> > +/**
> > + * Same as `git_config_bool`, except that it returns -1 on error rather
> > + * than dying.
> > + */
> >  int git_parse_maybe_bool(const char *);
> > +
> > +/**
> > + * Parse the string to an integer, including unit factors. Dies on error;
> > + * otherwise, returns the parsed result.
> > + */
> >  int git_config_int(const char *, const char *);
> >  int64_t git_config_int64(const char *, const char *);
> > +
> > +/**
> > + * Identical to `git_config_int`, but for unsigned longs.
> > + */
> >  unsigned long git_config_ulong(const char *, const char *);
> >  ssize_t git_config_ssize_t(const char *, const char *);
> > +
> > +/**
> > + * Same as `git_config_bool`, except that integers are returned as-is, and
> > + * an `is_bool` flag is unset.
> > + */
> >  int git_config_bool_or_int(const char *, const char *, int *);
> > +
> > +/**
> > + * Parse a string into a boolean value, respecting keywords like "true" and
> > + * "false". Integer values are converted into true/false values (when they
> > + * are non-zero or zero, respectively). Other values cause a die(). If
> > + * parsing is successful, the return value is the result.
> > + */
> >  int git_config_bool(const char *, const char *);
> > +
> > +/**
> > + * Allocates and copies the value string into the `dest` parameter; if no
> > + * string is given, prints an error message and returns -1.
> > + */
> >  int git_config_string(const char **, const char *, const char *);
> > +
> > +/**
> > + * Similar to `git_config_string`, but expands `~` or `~user` into the
> > + * user's home directory when found at the beginning of the path.
> > + */
> >  int git_config_pathname(const char **, const char *, const char *);
>
> I might like to see another space under this function so it's clear
> that the description isn't talking about expiry, color, or
> set_in_file_gently. There are other places where this comment applies,
> too.
Yes.
> >  int git_config_expiry_date(timestamp_t *, const char *, const char *);
> >  int git_config_color(char *, const char *, const char *);
> >  int git_config_set_in_file_gently(const char *, const char *, const char *);
> > +
> > +/**
> > + * write config values to a specific config file
> > + * takes a key/value pair as parameter.
> > + */
>
> You could reflow this comment and some others so that they extend closer
> to the end of the 80c line width; in some cases you can condense the
> comment to a single line this way :)
Ok.
> >  void git_config_set_in_file(const char *, const char *, const char *);
> >  int git_config_set_gently(const char *, const char *);
> > +
> > +/**
> > + * write config values to `.git/config`
> > + * takes a key/value pair as parameter.
> > + */
> >  void git_config_set(const char *, const char *);
> >  int git_config_parse_key(const char *, char **, int *);
> >  int git_config_key_is_valid(const char *key);
> >  int git_config_set_multivar_gently(const char *, const char *, const char *, int);
> >  void git_config_set_multivar(const char *, const char *, const char *, int);
> >  int git_config_set_multivar_in_file_gently(const char *, const char *, const char *, const char *, int);
> > +
> > +/**
> > + * takes four parameters:
> > + *
> > + * - the name of the file, as a string, to which key/value pairs will be written.
> > + *
> > + * - the name of key, as a string. This is in canonical "flat" form: the section,
> > + *   subsection, and variable segments will be separated by dots, and the section
> > + *   and variable segments will be all lowercase.
> > + *   E.g., `core.ignorecase`, `diff.SomeType.textconv`.
> > + *
> > + * - the value of the variable, as a string. If value is equal to NULL, it will
> > + *   remove the matching key from the config file.
> > + *
> > + * - the value regex, as a string. It will disregard key/value pairs where value
> > + *   does not match.
> > + *
> > + * - a multi_replace value, as an int. If value is equal to zero, nothing or only
> > + *   one matching key/value is replaced, else all matching key/values (regardless
> > + *   how many) are removed, before the new pair is written.
> > + *
> > + * It returns 0 on success.
> > + */
> >  void git_config_set_multivar_in_file(const char *, const char *, const char *, const char *, int);
> > +
> > +/**
> > + * rename or remove sections in the config file
> > + * parameters `old_name` and `new_name`
> > + * If NULL is passed through `new_name` parameter,
> > + * the section will be removed from the config file.
> > + */
> >  int git_config_rename_section(const char *, const char *);
> >  int git_config_rename_section_in_file(const char *, const char *, const char *);
> >  int git_config_copy_section(const char *, const char *);
> > @@ -142,6 +300,30 @@ enum config_scope current_config_scope(void);
> >  const char *current_config_origin_type(void);
> >  const char *current_config_name(void);
> >
> > +/**
> > + * Include Directives
> > + * ------------------
> > + *
> > + * By default, the config parser does not respect include directives.
> > + * However, a caller can use the special `git_config_include` wrapper
> > + * callback to support them. To do so, you simply wrap your "real" callback
> > + * function and data pointer in a `struct config_include_data`, and pass
> > + * the wrapper to the regular config-reading functions. For example:
> > + *
> > + * -------------------------------------------
> > + * int read_file_with_include(const char *file, config_fn_t fn, void *data)
> > + * {
> > + * struct config_include_data inc = CONFIG_INCLUDE_INIT;
> > + * inc.fn = fn;
> > + * inc.data = data;
> > + * return git_config_from_file(git_config_include, file, &inc);
> > + * }
> > + * -------------------------------------------
> > + *
> > + * `git_config` respects includes automatically. The lower-level
> > + * `git_config_from_file` does not.
> > + *
> > + */
> >  struct config_include_data {
> >       int depth;
> >       config_fn_t fn;
> > @@ -169,6 +351,33 @@ int parse_config_key(const char *var,
> >                    const char **subsection, int *subsection_len,
> >                    const char **key);
> >
> > +/**
> > + * Custom Configsets
> > + * -----------------
> > + *
> > + * A `config_set` can be used to construct an in-memory cache for
> > + * config-like files that the caller specifies (i.e., files like `.gitmodules`,
> > + * `~/.gitconfig` etc.). For example,
> > + *
> > + * ----------------------------------------
> > + * struct config_set gm_config;
> > + * git_configset_init(&gm_config);
> > + * int b;
> > + * //we add config files to the config_set
> > + * git_configset_add_file(&gm_config, ".gitmodules");
> > + * git_configset_add_file(&gm_config, ".gitmodules_alt");
> > + *
> > + * if (!git_configset_get_bool(gm_config, "submodule.frotz.ignore", &b)) {
> > + * //hack hack hack
> > + * }
> > + *
> > + * when we are done with the configset:
> > + * git_configset_clear(&gm_config);
> > + * ----------------------------------------
> > + *
> > + * Configset API provides functions for the above mentioned work flow
> > + */
> > +
> >  struct config_set_element {
> >       struct hashmap_entry ent;
> >       char *key;
> > @@ -197,15 +406,45 @@ struct config_set {
> >       struct configset_list list;
> >  };
> >
> > +/**
> > + * Initializes the config_set `cs`.
> > + */
> >  void git_configset_init(struct config_set *cs);
> > +
> > +/**
> > + * Parses the file and adds the variable-value pairs to the `config_set`,
> > + * dies if there is an error in parsing the file. Returns 0 on success, or
> > + * -1 if the file does not exist or is inaccessible. The user has to decide
> > + * if he wants to free the incomplete configset or continue using it when
> > + * the function returns -1.
> > + */
> >  int git_configset_add_file(struct config_set *cs, const char *filename);
> > +
> > +/**
> > + * Finds and returns the value list, sorted in order of increasing priority
> > + * for the configuration variable `key` and config set `cs`. When the
> > + * configuration variable `key` is not found, returns NULL. The caller
> > + * should not free or modify the returned pointer, as it is owned by the cache.
> > + */
> >  const struct string_list *git_configset_get_value_multi(struct config_set *cs, const char *key);
> > +
> > +/**
> > + * Clears `config_set` structure, removes all saved variable-value pairs.
> > + */
> >  void git_configset_clear(struct config_set *cs);
> >
> >  /*
> >   * These functions return 1 if not found, and 0 if found, leaving the found
> >   * value in the 'dest' pointer.
> >   */
> > +
> > +/*
> > + * Finds the highest-priority value for the configuration variable `key`
> > + * and config set `cs`, stores the pointer to it in `value` and returns 0.
> > + * When the configuration variable `key` is not found, returns 1 without
> > + * touching `value`. The caller should not free or modify `value`, as it
> > + * is owned by the cache.
> > + */
> >  int git_configset_get_value(struct config_set *cs, const char *key, const char **dest);
> >  int git_configset_get_string_const(struct config_set *cs, const char *key, const char **dest);
> >  int git_configset_get_string(struct config_set *cs, const char *key, char **dest);
> > @@ -240,16 +479,92 @@ int repo_config_get_maybe_bool(struct repository *repo,
> >  int repo_config_get_pathname(struct repository *repo,
> >                            const char *key, const char **dest);
> >
> > +/**
> > + * Querying For Specific Variables
> > + * -------------------------------
> > + *
> > + * For programs wanting to query for specific variables in a non-callback
> > + * manner, the config API provides two functions `git_config_get_value`
> > + * and `git_config_get_value_multi`. They both read values from an internal
> > + * cache generated previously from reading the config files.
> > + */
> > +
> > +/**
> > + * Finds the highest-priority value for the configuration variable `key`,
> > + * stores the pointer to it in `value` and returns 0. When the
> > + * configuration variable `key` is not found, returns 1 without touching
> > + * `value`. The caller should not free or modify `value`, as it is owned
> > + * by the cache.
> > + */
> >  int git_config_get_value(const char *key, const char **value);
> > +
> > +/**
> > + * Finds and returns the value list, sorted in order of increasing priority
> > + * for the configuration variable `key`. When the configuration variable
> > + * `key` is not found, returns NULL. The caller should not free or modify
> > + * the returned pointer, as it is owned by the cache.
> > + */
> >  const struct string_list *git_config_get_value_multi(const char *key);
> > +
> > +/**
> > + * Resets and invalidates the config cache.
> > + */
> >  void git_config_clear(void);
> > +
> > +/**
> > + * Allocates and copies the retrieved string into the `dest` parameter for
> > + * the configuration variable `key`; if NULL string is given, prints an
> > + * error message and returns -1. When the configuration variable `key` is
> > + * not found, returns 1 without touching `dest`.
> > + */
> >  int git_config_get_string_const(const char *key, const char **dest);
> > +
> > +/**
> > + * Similar to `git_config_get_string_const`, except that retrieved value
> > + * copied into the `dest` parameter is a mutable string.
> > + */
> >  int git_config_get_string(const char *key, char **dest);
> > +
> > +/**
> > + * Finds and parses the value to an integer for the configuration variable
> > + * `key`. Dies on error; otherwise, stores the value of the parsed integer in
> > + * `dest` and returns 0. When the configuration variable `key` is not found,
> > + * returns 1 without touching `dest`.
> > + */
> >  int git_config_get_int(const char *key, int *dest);
> > +
> > +/**
> > + * Similar to `git_config_get_int` but for unsigned longs.
> > + */
> >  int git_config_get_ulong(const char *key, unsigned long *dest);
> > +
> > +/**
> > + * Finds and parses the value into a boolean value, for the configuration
> > + * variable `key` respecting keywords like "true" and "false". Integer
> > + * values are converted into true/false values (when they are non-zero or
> > + * zero, respectively). Other values cause a die(). If parsing is successful,
> > + * stores the value of the parsed result in `dest` and returns 0. When the
> > + * configuration variable `key` is not found, returns 1 without touching
> > + * `dest`.
> > + */
> >  int git_config_get_bool(const char *key, int *dest);
> > +
> > +/**
> > + * Similar to `git_config_get_bool`, except that integers are copied as-is,
> > + * and `is_bool` flag is unset.
> > + */
> >  int git_config_get_bool_or_int(const char *key, int *is_bool, int *dest);
> > +
> > +/**
> > + * Similar to `git_config_get_bool`, except that it returns -1 on error
> > + * rather than dying.
> > + */
> >  int git_config_get_maybe_bool(const char *key, int *dest);
> > +
> > +/**
> > + * Similar to `git_config_get_string`, but expands `~` or `~user` into
> > + * the user's home directory when found at the beginning of the path.
> > + */
> >  int git_config_get_pathname(const char *key, const char **dest);
> >  int git_config_get_index_threads(int *dest);
> >  int git_config_get_untracked_cache(void);
> > @@ -270,7 +585,19 @@ struct key_value_info {
> >       enum config_scope scope;
> >  };
> >
> > +/**
> > + * First prints the error message specified by the caller in `err` and then
> > + * dies printing the line number and the file name of the highest priority
> > + * value for the configuration variable `key`.
> > + */
> >  NORETURN void git_die_config(const char *key, const char *err, ...) __attribute__((format(printf, 2, 3)));
> > +
> > +/**
> > + * Helper function which formats the die error message according to the
> > + * parameters entered. Used by `git_die_config()`. It can be used by callers
> > + * handling `git_config_get_value_multi()` to print the correct error message
> > + * for the desired value.
> > + */
> >  NORETURN void git_die_config_linenr(const char *key, const char *filename, int linenr);
> >
> >  #define LOOKUP_CONFIG(mapping, var) \
> > --
> > gitgitgadget
>
> I made a couple of smallish comments about general formatting, but I'm
> also interested to know whether you were able to move the entire
> contents of api-config.txt across to here. Was there anything that you
> couldn't find a place for?
Yes, everything is moved.
> Thanks a lot for this change, and congrats on getting your first review
> out! Welcome! :)
>
>  - Emily
>
Thanks a lot Emily for the detailed and helpful feedback!

Heba

  reply	other threads:[~2019-10-20  8:35 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-18  0:06 [PATCH 0/1] " Heba Waly via GitGitGadget
2019-10-18  0:06 ` [PATCH 1/1] " Heba Waly via GitGitGadget
2019-10-18 22:07   ` Jonathan Tan
2019-10-20  8:05     ` Heba Waly
2019-10-18 22:51   ` Emily Shaffer
2019-10-20  8:35     ` Heba Waly [this message]
2019-10-22 20:42       ` Emily Shaffer
2019-10-22  7:05 ` [PATCH v2 0/1] [Outreachy] config: move " Heba Waly via GitGitGadget
2019-10-22  7:05   ` [PATCH v2 1/1] " Heba Waly via GitGitGadget
2019-10-22 20:59     ` Emily Shaffer
2019-10-23  2:14       ` Junio C Hamano
2019-10-23  4:55       ` Heba Waly
2019-10-23  5:30   ` [PATCH v3 0/1] [Outreachy] " Heba Waly via GitGitGadget
2019-10-23  5:30     ` [PATCH v3 1/1] " Heba Waly via GitGitGadget
2019-10-23 21:38       ` Emily Shaffer
2019-10-24  2:14         ` Junio C Hamano

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