cheat/internal/sheets/gitdir.go

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package sheets
import (
"fmt"
"os"
"strings"
)
// isGitDir returns `true` if `path` is within a `.git` directory, or `false`
// otherwise
func isGitDir(path string) (bool, error) {
/*
A bit of context is called for here, because this functionality has
previously caused a number of tricky, subtle bugs.
Fundamentally, here we are simply trying to avoid walking over the
contents of the `.git` directory. Doing so potentially makes
hundreds/thousands of needless syscalls, and can noticeably harm
performance on machines with slow disks.
The earliest effort to solve this problem involved simply returning
`fs.SkipDir` when the cheatsheet file path began with `.`, signifying a
hidden directory. This, however, caused two problems:
1. The `.cheat` directory was ignored
2. Cheatsheets installed by `brew` (which were by default installed to
`~/.config/cheat`) were ignored
See: https://github.com/cheat/cheat/issues/690
To remedy this, the exclusion criteria were narrowed, and the search
for a literal `.` was replaced with a search for a literal `.git`.
This, however, broke user installations that stored cheatsheets in
`git` submodules, because such an installation would contain a `.git`
file that pointed to the upstream repository.
See: https://github.com/cheat/cheat/issues/694
Accounting for all of the above, we are now searching for the presence
of a `.git` literal string in the cheatsheet file path. If it is not
found, we continue to walk the directory, as before.
If it *is* found, we determine if `.git` refers to a file or directory,
and only stop walking the path in the latter case.
*/
// determine if the literal string `.git` appears within `path`
pos := strings.Index(path, ".git")
// if it does not, we know for certain that we are not within a `.git`
// directory.
if pos == -1 {
return false, nil
}
// If `path` does contain the string `.git`, we need to determine if we're
// inside of a `.git` directory, or if `path` points to a cheatsheet that's
// stored within a `git` submodule.
//
// See: https://github.com/cheat/cheat/issues/694
// truncate `path` to the occurrence of `.git`
f, err := os.Stat(path[:pos+4])
if err != nil {
return false, fmt.Errorf("failed to stat path %s: %v", path, err)
}
// return true or false depending on whether the truncated path is a
// directory
return f.Mode().IsDir(), nil
}