mirror of https://github.com/cheat/cheat.git
110 lines
3.9 KiB
Go
110 lines
3.9 KiB
Go
package repo
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import (
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"fmt"
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"os"
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"strings"
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)
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// GitDir returns `true` if we are iterating over a directory contained within
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// a repositories `.git` directory.
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func GitDir(path string) (bool, error) {
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/*
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A bit of context is called for here, because this functionality has
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previously caused a number of tricky, subtle bugs.
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Fundamentally, here we are simply trying to avoid walking over the
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contents of the `.git` directory. Doing so potentially makes
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hundreds/thousands of needless syscalls, and can noticeably harm
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performance on machines with slow disks.
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The earliest effort to solve this problem involved simply returning
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`fs.SkipDir` when the cheatsheet file path began with `.`, signifying a
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hidden directory. This, however, caused two problems:
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1. The `.cheat` directory was ignored
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2. Cheatsheets installed by `brew` (which were by default installed to
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`~/.config/cheat`) were ignored
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See: https://github.com/cheat/cheat/issues/690
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To remedy this, the exclusion criteria were narrowed, and the search
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for a literal `.` was replaced with a search for a literal `.git`.
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This, however, broke user installations that stored cheatsheets in
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`git` submodules, because such an installation would contain a `.git`
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file that pointed to the upstream repository.
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See: https://github.com/cheat/cheat/issues/694
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The next attempt at solving this was to search for a `.git` literal
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string in the cheatsheet file path. If a match was not found, we would
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continue to walk the directory, as before.
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If a match *was* found, we determined whether `.git` referred to a file
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or directory, and would only stop walking the path in the latter case.
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This, however, caused crashes if a cheatpath contained a `.gitignore`
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file. (Presumably, a crash would likewise occur on the presence of
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`.gitattributes`, `.gitmodules`, etc.)
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See: https://github.com/cheat/cheat/issues/699
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Accounting for all of the above (hopefully?), the current solution is
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not to search for `.git`, but `.git/` (including the directory
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separator), and then only ceasing to walk the directory on a match.
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To summarize, this code must account for the following possibilities:
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1. A cheatpath is not a repository
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2. A cheatpath is a repository
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3. A cheatpath is a repository, and contains a `.git*` file
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4. A cheatpath is a submodule
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Care must be taken to support the above on both Unix and Windows
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systems, which have different directory separators and line-endings.
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There is a lot of nuance to all of this, and it would be worthwhile to
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do two things to stop writing bugs here:
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1. Build integration tests around all of this
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2. Discard string-matching solutions entirely, and use `go-git` instead
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NB: A reasonable smoke-test for ensuring that skipping is being applied
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correctly is to run the following command:
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make && strace ./dist/cheat -l | wc -l
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That check should be run twice: once normally, and once after
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commenting out the "skip" check in `sheets.Load`.
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The specific line counts don't matter; what matters is that the number
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of syscalls should be significantly lower with the skip check enabled.
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*/
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// determine if the literal string `.git` appears within `path`
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pos := strings.Index(path, fmt.Sprintf(".git%s", string(os.PathSeparator)))
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// if it does not, we know for certain that we are not within a `.git`
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// directory.
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if pos == -1 {
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return false, nil
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}
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// If `path` does contain the string `.git`, we need to determine if we're
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// inside of a `.git` directory, or if `path` points to a cheatsheet that's
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// stored within a `git` submodule.
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//
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// See: https://github.com/cheat/cheat/issues/694
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// truncate `path` to the occurrence of `.git`
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f, err := os.Stat(path[:pos+5])
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if err != nil {
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return false, fmt.Errorf("failed to stat path %s: %v", path, err)
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}
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// return true or false depending on whether the truncated path is a
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// directory
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return f.Mode().IsDir(), nil
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}
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