The API in remote.h gives access to the configuration related to remotes. It handles all three configuration mechanisms historically and currently used by git, and presents the information in a uniform fashion. Note that the code also handles plain URLs without any configuration, giving them just the default information.
The user’s nickname for the remote
An array of all of the url_nr URLs configured for the remote
An array of refspecs configured for pushing, with push_refspec being the literal strings, and push_refspec_nr being the quantity.
An array of refspecs configured for fetching, with fetch_refspec being the literal strings, and fetch_refspec_nr being the quantity.
The setting for whether to fetch tags (as a separate rule from the configured refspecs); -1 means never to fetch tags, 0 means to auto-follow tags based on the default heuristic, 1 means to always auto-follow tags, and 2 means to fetch all tags.
The configured helper programs to run on the remote side, for git-native protocols.
The proxy to use for curl (http, https, ftp, etc.) URLs.
struct remotes can be found by name with remote_get(), and iterated through with for_each_remote(). remote_get(NULL) will return the default remote, given the current branch and configuration.
A struct refspec holds the parsed interpretation of a refspec. If it will force updates (starts with a +), force is true. If it is a pattern (sides end with *) pattern is true. src and dest are the two sides (if a pattern, only the part outside of the wildcards); if there is only one side, it is src, and dst is NULL; if sides exist but are empty (i.e., the refspec either starts or ends with :), the corresponding side is "".
This parsing can be done to an array of strings to give an array of struct refpsecs with parse_ref_spec().
remote_find_tracking(), given a remote and a struct refspec with either src or dst filled out, will fill out the other such that the result is in the "fetch" specification for the remote (note that this evaluates patterns and returns a single result).
Note that this may end up moving to branch.h
struct branch holds the configuration for a branch. It can be looked branch_get(NULL) for HEAD.
The short name of the branch.
The full path for the branch ref.
The name of the remote listed in the configuration.
The struct remote for that remote.
An array of the "merge" lines in the configuration.
An array of the struct refspecs used for the merge lines. That is, merge[i]→dst is a local tracking ref which should be merged into this branch by default.
The number of merge configurations
branch_has_merge_config() returns true if the given branch has merge configuration given.
There is other stuff in remote.h that is related, in general, to the process of interacting with remotes.