Git has the cat-file command to inspect internal files, e.g. git cat-file blob 557db03 will show the contents of the object whose hash starts with 557db03.
Are there similar tools for mercurial that allow me to look at all the different data files that merfcurial uses internally?
Try hg --debug help and you can see the list of all the debug commands:
debugancestor:
find the ancestor revision of two revisions in a given index
debugbuilddag:
builds a repo with a given DAG from scratch in the current empty repo
debugbundle:
lists the contents of a bundle
debugcheckstate:
validate the correctness of the current dirstate
debugcommands:
list all available commands and options
debugcomplete:
returns the completion list associated with the given command
debugdag:
format the changelog or an index DAG as a concise textual description
debugdata:
dump the contents of a data file revision
debugdate:
parse and display a date
debugdiscovery:
runs the changeset discovery protocol in isolation
debugfileset:
parse and apply a fileset specification
debugfsinfo:
show information detected about current filesystem
debuggetbundle:
retrieves a bundle from a repo
debugignore:
display the combined ignore pattern
debugindex:
dump the contents of an index file
debugindexdot:
dump an index DAG as a graphviz dot file
debuginstall:
test Mercurial installation
debugknown:
test whether node ids are known to a repo
debugpushkey:
access the pushkey key/value protocol
debugrebuildstate:
rebuild the dirstate as it would look like for the given revision
debugrename:
dump rename information
debugrevlog:
show data and statistics about a revlog
debugrevspec:
parse and apply a revision specification
debugsetparents:
manually set the parents of the current working directory
debugstate:
show the contents of the current dirstate
debugsub:
(no help text available)
debugwalk:
show how files match on given patterns
debugwireargs:
(no help text available)
There are a lot of them, and they pretty much expose everything.