1 files changed, 71 insertions, 0 deletions

diff --git a/cli/internal/doublestar/utils.go b/cli/internal/doublestar/utils.go
new file mode 100644
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--- /dev/null
+++ b/cli/internal/doublestar/utils.go
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+// Package doublestar is adapted from https://github.com/bmatcuk/doublestar
+// Copyright Bob Matcuk. All Rights Reserved.
+// SPDX-License-Identifier: MIT
+package doublestar
+
+// SplitPattern is a utility function. Given a pattern, SplitPattern will
+// return two strings: the first string is everything up to the last slash
+// (`/`) that appears _before_ any unescaped "meta" characters (ie, `*?[{`).
+// The second string is everything after that slash. For example, given the
+// pattern:
+//
+//	../../path/to/meta*/**
+//	             ^----------- split here
+//
+// SplitPattern returns "../../path/to" and "meta*/**". This is useful for
+// initializing os.DirFS() to call Glob() because Glob() will silently fail if
+// your pattern includes `/./` or `/../`. For example:
+//
+//	base, pattern := SplitPattern("../../path/to/meta*/**")
+//	fsys := os.DirFS(base)
+//	matches, err := Glob(fsys, pattern)
+//
+// If SplitPattern cannot find somewhere to split the pattern (for example,
+// `meta*/**`), it will return "." and the unaltered pattern (`meta*/**` in
+// this example).
+//
+// Of course, it is your responsibility to decide if the returned base path is
+// "safe" in the context of your application. Perhaps you could use Match() to
+// validate against a list of approved base directories?
+func SplitPattern(p string) (string, string) {
+	base := "."
+	pattern := p
+
+	splitIdx := -1
+	for i := 0; i < len(p); i++ {
+		c := p[i]
+		if c == '\\' {
+			i++
+		} else if c == '/' {
+			splitIdx = i
+		} else if c == '*' || c == '?' || c == '[' || c == '{' {
+			break
+		}
+	}
+
+	if splitIdx >= 0 {
+		return p[:splitIdx], p[splitIdx+1:]
+	}
+
+	return base, pattern
+}
+
+// Finds the next comma, but ignores any commas that appear inside nested `{}`.
+// Assumes that each opening bracket has a corresponding closing bracket.
+func indexNextAlt(s string, allowEscaping bool) int {
+	alts := 1
+	l := len(s)
+	for i := 0; i < l; i++ {
+		if allowEscaping && s[i] == '\\' {
+			// skip next byte
+			i++
+		} else if s[i] == '{' {
+			alts++
+		} else if s[i] == '}' {
+			alts--
+		} else if s[i] == ',' && alts == 1 {
+			return i
+		}
+	}
+	return -1
+}