doc: added documentation to all functions

src/db/git.v

@@ -153,6 +153,8 @@ pub fn (db &VieterDb) update_git_repo_archs(repo_id int, archs []GitRepoArch) {
 	}
 }
 
+// git_repo_exists is a utility function that checks whether a repo with the
+// given id exists.
 pub fn (db &VieterDb) git_repo_exists(repo_id int) bool {
 	db.get_git_repo(repo_id) or { return false }
 

src/db/logs.v

@@ -12,6 +12,7 @@ pub:
 	exit_code  int       [nonull]
 }
 
+// str returns a string representation.
 pub fn (bl &BuildLog) str() string {
 	mut parts := [
 		'id: $bl.id',