Work on adding ignorefiles support to choose-files

tools/ignorefiles/api.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"io"
 	"io/fs"
+	"sync"
 )
 
 var _ = fmt.Print
@@ -16,10 +17,15 @@ type IgnoreFile interface {
 	LoadPath(string) error
 
 	// relpath is the path relative to the directory containing the ignorefile.
-	// When is_ignored is true, linenum_of_matching_rule will be the line
-	// number of the rule causing relpath to be ignored and pattern is the
-	// textual representation of the matching pattern.
+	// When the result is due to a rule matching, linenum_of_matching_rule is
+	// >=0 and pattern is the textual representation of the rule. Otherwise
+	// linenum_of_matching_rule is -1 and pattern is the empty string.
 	IsIgnored(relpath string, ftype fs.FileMode) (is_ignored bool, linenum_of_matching_rule int, pattern string)
 }
 
 func NewGitignore() IgnoreFile { return &Gitignore{index_of_last_negated_rule: -1} }
+
+// The global gitignore from ~/.config/git/ignore
+var GlobalGitignore = sync.OnceValue(func() IgnoreFile {
+	return get_global_gitignore()
+})

tools/ignorefiles/gitignore.go

@@ -41,8 +41,8 @@ func (g Gitignore) IsIgnored(relpath string, ftype os.FileMode) (is_ignored bool
 			}
 			if pat.negated && pat.Match(relpath, ftype) {
 				is_ignored = false
-				linenum_of_matching_rule = -1
-				pattern = ""
+				linenum_of_matching_rule = pat.line_number
+				pattern = pat.pattern
 			}
 		} else {
 			if !pat.negated && pat.Match(relpath, ftype) {
@@ -257,3 +257,45 @@ func CompileGitIgnoreLine(line string) (ans GitPattern, skipped_line bool) {
 	}
 	return
 }
+
+func get_global_gitconfig_excludesfile() (ans string) {
+	cfhome := os.Getenv("XDG_CONFIG_HOME")
+	if cfhome == "" {
+		cfhome = utils.Expanduser("~/.config")
+	}
+	for _, candidate := range []string{"/etc/gitconfig", filepath.Join(cfhome, "git", "config"), utils.Expanduser("~/.gitconfig")} {
+		if data, err := os.ReadFile(candidate); err == nil {
+			s := utils.NewLineScanner(utils.UnsafeBytesToString(data))
+			in_core := false
+			for s.Scan() {
+				line := strings.TrimSpace(s.Text())
+				if in_core {
+					if strings.HasPrefix(line, "[") {
+						in_core = false
+						continue
+					}
+					if k, rest, found := strings.Cut(line, "="); found && strings.ToLower(strings.TrimSpace(k)) == `excludesfile` {
+						ans = strings.TrimSpace(rest)
+					}
+				} else if strings.ToLower(line) == "[core]" {
+					in_core = true
+				}
+			}
+		}
+	}
+	if ans == "" {
+		ans = filepath.Join(cfhome, "git", "ignore")
+	}
+	return
+}
+
+func get_global_gitignore() (ans IgnoreFile) {
+	excludesfile := get_global_gitconfig_excludesfile()
+	if data, err := os.ReadFile(excludesfile); err == nil {
+		q := NewGitignore()
+		if q.LoadString(utils.UnsafeBytesToString(data)) == nil {
+			ans = q
+		}
+	}
+	return
+}