git: find main branch from config

deps: bump go-git

config: server host and port

templates: tree and log links for tags

routes: refs view

routes: index view

routes: render readme

templates: fix 404 and 500

template: render diff header lines

git, routes: commit diff view

routes, templates: tree and log views

git: fix trees

routes: file content view

git: file content at ref

routes: split repo index and files views

git: fetch files only using ref

all: init