1 files changed, 507 insertions, 0 deletions

diff --git a/userdiff.c b/userdiff.c
new file mode 100644
index 0000000..e399543
--- /dev/null
+++ b/userdiff.c
@@ -0,0 +1,507 @@
+#include "git-compat-util.h"
+#include "config.h"
+#include "userdiff.h"
+#include "attr.h"
+#include "strbuf.h"
+
+static struct userdiff_driver *drivers;
+static int ndrivers;
+static int drivers_alloc;
+
+#define PATTERNS(lang, rx, wrx) { \
+	.name = lang, \
+	.binary = -1, \
+	.funcname = { \
+		.pattern = rx, \
+		.cflags = REG_EXTENDED, \
+	}, \
+	.word_regex = wrx "|[^[:space:]]|[\xc0-\xff][\x80-\xbf]+", \
+	.word_regex_multi_byte = wrx "|[^[:space:]]", \
+}
+#define IPATTERN(lang, rx, wrx) { \
+	.name = lang, \
+	.binary = -1, \
+	.funcname = { \
+		.pattern = rx, \
+		.cflags = REG_EXTENDED | REG_ICASE, \
+	}, \
+	.word_regex = wrx "|[^[:space:]]|[\xc0-\xff][\x80-\xbf]+", \
+	.word_regex_multi_byte = wrx "|[^[:space:]]", \
+}
+
+/*
+ * Built-in drivers for various languages, sorted by their names
+ * (except that the "default" is left at the end).
+ *
+ * When writing or updating patterns, assume that the contents these
+ * patterns are applied to are syntactically correct.  The patterns
+ * can be simple without implementing all syntactical corner cases, as
+ * long as they are sufficiently permissive.
+ */
+static struct userdiff_driver builtin_drivers[] = {
+IPATTERN("ada",
+	 "!^(.*[ \t])?(is[ \t]+new|renames|is[ \t]+separate)([ \t].*)?$\n"
+	 "!^[ \t]*with[ \t].*$\n"
+	 "^[ \t]*((procedure|function)[ \t]+.*)$\n"
+	 "^[ \t]*((package|protected|task)[ \t]+.*)$",
+	 /* -- */
+	 "[a-zA-Z][a-zA-Z0-9_]*"
+	 "|[-+]?[0-9][0-9#_.aAbBcCdDeEfF]*([eE][+-]?[0-9_]+)?"
+	 "|=>|\\.\\.|\\*\\*|:=|/=|>=|<=|<<|>>|<>"),
+PATTERNS("bash",
+	 /* Optional leading indentation */
+	 "^[ \t]*"
+	 /* Start of captured text */
+	 "("
+	 "("
+	     /* POSIX identifier with mandatory parentheses */
+	     "[a-zA-Z_][a-zA-Z0-9_]*[ \t]*\\([ \t]*\\))"
+	 "|"
+	     /* Bashism identifier with optional parentheses */
+	     "(function[ \t]+[a-zA-Z_][a-zA-Z0-9_]*(([ \t]*\\([ \t]*\\))|([ \t]+))"
+	 ")"
+	 /* Optional whitespace */
+	 "[ \t]*"
+	 /* Compound command starting with `{`, `(`, `((` or `[[` */
+	 "(\\{|\\(\\(?|\\[\\[)"
+	 /* End of captured text */
+	 ")",
+	 /* -- */
+	 /* Characters not in the default $IFS value */
+	 "[^ \t]+"),
+PATTERNS("bibtex",
+	 "(@[a-zA-Z]{1,}[ \t]*\\{{0,1}[ \t]*[^ \t\"@',\\#}{~%]*).*$",
+	 /* -- */
+	 "[={}\"]|[^={}\" \t]+"),
+PATTERNS("cpp",
+	 /* Jump targets or access declarations */
+	 "!^[ \t]*[A-Za-z_][A-Za-z_0-9]*:[[:space:]]*($|/[/*])\n"
+	 /* functions/methods, variables, and compounds at top level */
+	 "^((::[[:space:]]*)?[A-Za-z_].*)$",
+	 /* -- */
+	 /* identifiers and keywords */
+	 "[a-zA-Z_][a-zA-Z0-9_]*"
+	 /* decimal and octal integers as well as floatingpoint numbers */
+	 "|[0-9][0-9.]*([Ee][-+]?[0-9]+)?[fFlLuU]*"
+	 /* hexadecimal and binary integers */
+	 "|0[xXbB][0-9a-fA-F]+[lLuU]*"
+	 /* floatingpoint numbers that begin with a decimal point */
+	 "|\\.[0-9][0-9]*([Ee][-+]?[0-9]+)?[fFlL]?"
+	 "|[-+*/<>%&^|=!]=|--|\\+\\+|<<=?|>>=?|&&|\\|\\||::|->\\*?|\\.\\*|<=>"),
+PATTERNS("csharp",
+	 /* Keywords */
+	 "!^[ \t]*(do|while|for|if|else|instanceof|new|return|switch|case|throw|catch|using)\n"
+	 /* Methods and constructors */
+	 "^[ \t]*(((static|public|internal|private|protected|new|virtual|sealed|override|unsafe|async)[ \t]+)*[][<>@.~_[:alnum:]]+[ \t]+[<>@._[:alnum:]]+[ \t]*\\(.*\\))[ \t]*$\n"
+	 /* Properties */
+	 "^[ \t]*(((static|public|internal|private|protected|new|virtual|sealed|override|unsafe)[ \t]+)*[][<>@.~_[:alnum:]]+[ \t]+[@._[:alnum:]]+)[ \t]*$\n"
+	 /* Type definitions */
+	 "^[ \t]*(((static|public|internal|private|protected|new|unsafe|sealed|abstract|partial)[ \t]+)*(class|enum|interface|struct|record)[ \t]+.*)$\n"
+	 /* Namespace */
+	 "^[ \t]*(namespace[ \t]+.*)$",
+	 /* -- */
+	 "[a-zA-Z_][a-zA-Z0-9_]*"
+	 "|[-+0-9.e]+[fFlL]?|0[xXbB]?[0-9a-fA-F]+[lL]?"
+	 "|[-+*/<>%&^|=!]=|--|\\+\\+|<<=?|>>=?|&&|\\|\\||::|->"),
+IPATTERN("css",
+	 "![:;][[:space:]]*$\n"
+	 "^[:[@.#]?[_a-z0-9].*$",
+	 /* -- */
+	 /*
+	  * This regex comes from W3C CSS specs. Should theoretically also
+	  * allow ISO 10646 characters U+00A0 and higher,
+	  * but they are not handled in this regex.
+	  */
+	 "-?[_a-zA-Z][-_a-zA-Z0-9]*" /* identifiers */
+	 "|-?[0-9]+|\\#[0-9a-fA-F]+" /* numbers */
+),
+PATTERNS("dts",
+	 "!;\n"
+	 "!=\n"
+	 /* lines beginning with a word optionally preceded by '&' or the root */
+	 "^[ \t]*((/[ \t]*\\{|&?[a-zA-Z_]).*)",
+	 /* -- */
+	 /* Property names and math operators */
+	 "[a-zA-Z0-9,._+?#-]+"
+	 "|[-+*/%&^|!~]|>>|<<|&&|\\|\\|"),
+PATTERNS("elixir",
+	 "^[ \t]*((def(macro|module|impl|protocol|p)?|test)[ \t].*)$",
+	 /* -- */
+	 /* Atoms, names, and module attributes */
+	 "[@:]?[a-zA-Z0-9@_?!]+"
+	 /* Numbers with specific base */
+	 "|[-+]?0[xob][0-9a-fA-F]+"
+	 /* Numbers */
+	 "|[-+]?[0-9][0-9_.]*([eE][-+]?[0-9_]+)?"
+	 /* Operators and atoms that represent them */
+	 "|:?(\\+\\+|--|\\.\\.|~~~|<>|\\^\\^\\^|<?\\|>|<<<?|>?>>|<<?~|~>?>|<~>|<=|>=|===?|!==?|=~|&&&?|\\|\\|\\|?|=>|<-|\\\\\\\\|->)"
+	 /* Not real operators, but should be grouped */
+	 "|:?%[A-Za-z0-9_.]\\{\\}?"),
+IPATTERN("fortran",
+	 /* Don't match comment lines */
+	 "!^([C*]|[ \t]*!)\n"
+	 /* Don't match 'module procedure' lines */
+	 "!^[ \t]*MODULE[ \t]+PROCEDURE[ \t]\n"
+	 /* Program, module, block data */
+	 "^[ \t]*((END[ \t]+)?(PROGRAM|MODULE|BLOCK[ \t]+DATA"
+		/* Subroutines and functions */
+		"|([^!'\" \t]+[ \t]+)*(SUBROUTINE|FUNCTION))[ \t]+[A-Z].*)$",
+	 /* -- */
+	 "[a-zA-Z][a-zA-Z0-9_]*"
+	 "|\\.([Ee][Qq]|[Nn][Ee]|[Gg][TtEe]|[Ll][TtEe]|[Tt][Rr][Uu][Ee]|[Ff][Aa][Ll][Ss][Ee]|[Aa][Nn][Dd]|[Oo][Rr]|[Nn]?[Ee][Qq][Vv]|[Nn][Oo][Tt])\\."
+	 /* numbers and format statements like 2E14.4, or ES12.6, 9X.
+	  * Don't worry about format statements without leading digits since
+	  * they would have been matched above as a variable anyway. */
+	 "|[-+]?[0-9.]+([AaIiDdEeFfLlTtXx][Ss]?[-+]?[0-9.]*)?(_[a-zA-Z0-9][a-zA-Z0-9_]*)?"
+	 "|//|\\*\\*|::|[/<>=]="),
+IPATTERN("fountain",
+	 "^((\\.[^.]|(int|ext|est|int\\.?/ext|i/e)[. ]).*)$",
+	 /* -- */
+	 "[^ \t-]+"),
+PATTERNS("golang",
+	 /* Functions */
+	 "^[ \t]*(func[ \t]*.*(\\{[ \t]*)?)\n"
+	 /* Structs and interfaces */
+	 "^[ \t]*(type[ \t].*(struct|interface)[ \t]*(\\{[ \t]*)?)",
+	 /* -- */
+	 "[a-zA-Z_][a-zA-Z0-9_]*"
+	 "|[-+0-9.eE]+i?|0[xX]?[0-9a-fA-F]+i?"
+	 "|[-+*/<>%&^|=!:]=|--|\\+\\+|<<=?|>>=?|&\\^=?|&&|\\|\\||<-|\\.{3}"),
+PATTERNS("html",
+	 "^[ \t]*(<[Hh][1-6]([ \t].*)?>.*)$",
+	 /* -- */
+	 "[^<>= \t]+"),
+PATTERNS("java",
+	 "!^[ \t]*(catch|do|for|if|instanceof|new|return|switch|throw|while)\n"
+	 /* Class, enum, interface, and record declarations */
+	 "^[ \t]*(([a-z-]+[ \t]+)*(class|enum|interface|record)[ \t]+.*)$\n"
+	 /* Method definitions; note that constructor signatures are not */
+	 /* matched because they are indistinguishable from method calls. */
+	 "^[ \t]*(([A-Za-z_<>&][][?&<>.,A-Za-z_0-9]*[ \t]+)+[A-Za-z_][A-Za-z_0-9]*[ \t]*\\([^;]*)$",
+	 /* -- */
+	 "[a-zA-Z_][a-zA-Z0-9_]*"
+	 "|[-+0-9.e]+[fFlL]?|0[xXbB]?[0-9a-fA-F]+[lL]?"
+	 "|[-+*/<>%&^|=!]="
+	 "|--|\\+\\+|<<=?|>>>?=?|&&|\\|\\|"),
+PATTERNS("kotlin",
+	 "^[ \t]*(([a-z]+[ \t]+)*(fun|class|interface)[ \t]+.*)$",
+	 /* -- */
+	 "[a-zA-Z_][a-zA-Z0-9_]*"
+	 /* hexadecimal and binary numbers */
+	 "|0[xXbB][0-9a-fA-F_]+[lLuU]*"
+	 /* integers and floats */
+	 "|[0-9][0-9_]*([.][0-9_]*)?([Ee][-+]?[0-9]+)?[fFlLuU]*"
+	 /* floating point numbers beginning with decimal point */
+	 "|[.][0-9][0-9_]*([Ee][-+]?[0-9]+)?[fFlLuU]?"
+	 /* unary and binary operators */
+	 "|[-+*/<>%&^|=!]==?|--|\\+\\+|<<=|>>=|&&|\\|\\||->|\\.\\*|!!|[?:.][.:]"),
+PATTERNS("markdown",
+	 "^ {0,3}#{1,6}[ \t].*",
+	 /* -- */
+	 "[^<>= \t]+"),
+PATTERNS("matlab",
+	 /*
+	  * Octave pattern is mostly the same as matlab, except that '%%%' and
+	  * '##' can also be used to begin code sections, in addition to '%%'
+	  * that is understood by both.
+	  */
+	 "^[[:space:]]*((classdef|function)[[:space:]].*)$|^(%%%?|##)[[:space:]].*$",
+	 /* -- */
+	 "[a-zA-Z_][a-zA-Z0-9_]*|[-+0-9.e]+|[=~<>]=|\\.[*/\\^']|\\|\\||&&"),
+PATTERNS("objc",
+	 /* Negate C statements that can look like functions */
+	 "!^[ \t]*(do|for|if|else|return|switch|while)\n"
+	 /* Objective-C methods */
+	 "^[ \t]*([-+][ \t]*\\([ \t]*[A-Za-z_][A-Za-z_0-9* \t]*\\)[ \t]*[A-Za-z_].*)$\n"
+	 /* C functions */
+	 "^[ \t]*(([A-Za-z_][A-Za-z_0-9]*[ \t]+)+[A-Za-z_][A-Za-z_0-9]*[ \t]*\\([^;]*)$\n"
+	 /* Objective-C class/protocol definitions */
+	 "^(@(implementation|interface|protocol)[ \t].*)$",
+	 /* -- */
+	 "[a-zA-Z_][a-zA-Z0-9_]*"
+	 "|[-+0-9.e]+[fFlL]?|0[xXbB]?[0-9a-fA-F]+[lL]?"
+	 "|[-+*/<>%&^|=!]=|--|\\+\\+|<<=?|>>=?|&&|\\|\\||::|->"),
+PATTERNS("pascal",
+	 "^(((class[ \t]+)?(procedure|function)|constructor|destructor|interface"
+	 "|implementation|initialization|finalization)[ \t]*.*)$\n"
+	 "^(.*=[ \t]*(class|record).*)$",
+	 /* -- */
+	 "[a-zA-Z_][a-zA-Z0-9_]*"
+	 "|[-+0-9.e]+|0[xXbB]?[0-9a-fA-F]+"
+	 "|<>|<=|>=|:=|\\.\\."),
+PATTERNS("perl",
+	 "^package .*\n"
+	 "^sub [[:alnum:]_':]+[ \t]*"
+		"(\\([^)]*\\)[ \t]*)?" /* prototype */
+		/*
+		 * Attributes.  A regex can't count nested parentheses,
+		 * so just slurp up whatever we see, taking care not
+		 * to accept lines like "sub foo; # defined elsewhere".
+		 *
+		 * An attribute could contain a semicolon, but at that
+		 * point it seems reasonable enough to give up.
+		 */
+		"(:[^;#]*)?"
+		"(\\{[ \t]*)?" /* brace can come here or on the next line */
+		"(#.*)?$\n" /* comment */
+	 "^(BEGIN|END|INIT|CHECK|UNITCHECK|AUTOLOAD|DESTROY)[ \t]*"
+		"(\\{[ \t]*)?" /* brace can come here or on the next line */
+		"(#.*)?$\n"
+	 "^=head[0-9] .*",	/* POD */
+	 /* -- */
+	 "[[:alpha:]_'][[:alnum:]_']*"
+	 "|0[xb]?[0-9a-fA-F_]*"
+	 /* taking care not to interpret 3..5 as (3.)(.5) */
+	 "|[0-9a-fA-F_]+(\\.[0-9a-fA-F_]+)?([eE][-+]?[0-9_]+)?"
+	 "|=>|-[rwxoRWXOezsfdlpSugkbctTBMAC>]|~~|::"
+	 "|&&=|\\|\\|=|//=|\\*\\*="
+	 "|&&|\\|\\||//|\\+\\+|--|\\*\\*|\\.\\.\\.?"
+	 "|[-+*/%.^&<>=!|]="
+	 "|=~|!~"
+	 "|<<|<>|<=>|>>"),
+PATTERNS("php",
+	 "^[\t ]*(((public|protected|private|static|abstract|final)[\t ]+)*function.*)$\n"
+	 "^[\t ]*((((final|abstract)[\t ]+)?class|enum|interface|trait).*)$",
+	 /* -- */
+	 "[a-zA-Z_][a-zA-Z0-9_]*"
+	 "|[-+0-9.e]+|0[xXbB]?[0-9a-fA-F]+"
+	 "|[-+*/<>%&^|=!.]=|--|\\+\\+|<<=?|>>=?|===|&&|\\|\\||::|->"),
+PATTERNS("python",
+	 "^[ \t]*((class|(async[ \t]+)?def)[ \t].*)$",
+	 /* -- */
+	 "[a-zA-Z_][a-zA-Z0-9_]*"
+	 "|[-+0-9.e]+[jJlL]?|0[xX]?[0-9a-fA-F]+[lL]?"
+	 "|[-+*/<>%&^|=!]=|//=?|<<=?|>>=?|\\*\\*=?"),
+	 /* -- */
+PATTERNS("ruby",
+	 "^[ \t]*((class|module|def)[ \t].*)$",
+	 /* -- */
+	 "(@|@@|\\$)?[a-zA-Z_][a-zA-Z0-9_]*"
+	 "|[-+0-9.e]+|0[xXbB]?[0-9a-fA-F]+|\\?(\\\\C-)?(\\\\M-)?."
+	 "|//=?|[-+*/<>%&^|=!]=|<<=?|>>=?|===|\\.{1,3}|::|[!=]~"),
+PATTERNS("rust",
+	 "^[\t ]*((pub(\\([^\\)]+\\))?[\t ]+)?((async|const|unsafe|extern([\t ]+\"[^\"]+\"))[\t ]+)?(struct|enum|union|mod|trait|fn|impl|macro_rules!)[< \t]+[^;]*)$",
+	 /* -- */
+	 "[a-zA-Z_][a-zA-Z0-9_]*"
+	 "|[0-9][0-9_a-fA-Fiosuxz]*(\\.([0-9]*[eE][+-]?)?[0-9_fF]*)?"
+	 "|[-+*\\/<>%&^|=!:]=|<<=?|>>=?|&&|\\|\\||->|=>|\\.{2}=|\\.{3}|::"),
+PATTERNS("scheme",
+	 "^[\t ]*(\\(((define|def(struct|syntax|class|method|rules|record|proto|alias)?)[-*/ \t]|(library|module|struct|class)[*+ \t]).*)$",
+	 /*
+	  * R7RS valid identifiers include any sequence enclosed
+	  * within vertical lines having no backslashes
+	  */
+	 "\\|([^\\\\]*)\\|"
+	 /* All other words should be delimited by spaces or parentheses */
+	 "|([^][)(}{[ \t])+"),
+PATTERNS("tex", "^(\\\\((sub)*section|chapter|part)\\*{0,1}\\{.*)$",
+	 "\\\\[a-zA-Z@]+|\\\\.|([a-zA-Z0-9]|[^\x01-\x7f])+"),
+{ "default", NULL, NULL, -1, { NULL, 0 } },
+};
+#undef PATTERNS
+#undef IPATTERN
+
+static struct userdiff_driver driver_true = {
+	.name = "diff=true",
+	.binary = 0,
+};
+
+static struct userdiff_driver driver_false = {
+	.name = "!diff",
+	.binary = 1,
+};
+
+struct find_by_namelen_data {
+	const char *name;
+	size_t len;
+	struct userdiff_driver *driver;
+};
+
+static int userdiff_find_by_namelen_cb(struct userdiff_driver *driver,
+				       enum userdiff_driver_type type UNUSED,
+				       void *priv)
+{
+	struct find_by_namelen_data *cb_data = priv;
+
+	if (!strncmp(driver->name, cb_data->name, cb_data->len) &&
+	    !driver->name[cb_data->len]) {
+		cb_data->driver = driver;
+		return 1; /* tell the caller to stop iterating */
+	}
+	return 0;
+}
+
+static int regexec_supports_multi_byte_chars(void)
+{
+	static const char not_space[] = "[^[:space:]]";
+	static const char utf8_multi_byte_char[] = "\xc2\xa3";
+	regex_t re;
+	regmatch_t match;
+	static int result = -1;
+
+	if (result != -1)
+		return result;
+	if (regcomp(&re, not_space, REG_EXTENDED))
+		BUG("invalid regular expression: %s", not_space);
+	result = !regexec(&re, utf8_multi_byte_char, 1, &match, 0) &&
+		match.rm_so == 0 &&
+		match.rm_eo == strlen(utf8_multi_byte_char);
+	regfree(&re);
+	return result;
+}
+
+static struct userdiff_driver *userdiff_find_by_namelen(const char *name, size_t len)
+{
+	struct find_by_namelen_data udcbdata = {
+		.name = name,
+		.len = len,
+	};
+	for_each_userdiff_driver(userdiff_find_by_namelen_cb, &udcbdata);
+	return udcbdata.driver;
+}
+
+static int parse_funcname(struct userdiff_funcname *f, const char *k,
+		const char *v, int cflags)
+{
+	if (git_config_string(&f->pattern, k, v) < 0)
+		return -1;
+	f->cflags = cflags;
+	return 0;
+}
+
+static int parse_tristate(int *b, const char *k, const char *v)
+{
+	if (v && !strcasecmp(v, "auto"))
+		*b = -1;
+	else
+		*b = git_config_bool(k, v);
+	return 0;
+}
+
+static int parse_bool(int *b, const char *k, const char *v)
+{
+	*b = git_config_bool(k, v);
+	return 0;
+}
+
+int userdiff_config(const char *k, const char *v)
+{
+	struct userdiff_driver *drv;
+	const char *name, *type;
+	size_t namelen;
+
+	if (parse_config_key(k, "diff", &name, &namelen, &type) || !name)
+		return 0;
+
+	drv = userdiff_find_by_namelen(name, namelen);
+	if (!drv) {
+		ALLOC_GROW(drivers, ndrivers+1, drivers_alloc);
+		drv = &drivers[ndrivers++];
+		memset(drv, 0, sizeof(*drv));
+		drv->name = xmemdupz(name, namelen);
+		drv->binary = -1;
+	}
+
+	if (!strcmp(type, "funcname"))
+		return parse_funcname(&drv->funcname, k, v, 0);
+	if (!strcmp(type, "xfuncname"))
+		return parse_funcname(&drv->funcname, k, v, REG_EXTENDED);
+	if (!strcmp(type, "binary"))
+		return parse_tristate(&drv->binary, k, v);
+	if (!strcmp(type, "command"))
+		return git_config_string(&drv->external, k, v);
+	if (!strcmp(type, "textconv"))
+		return git_config_string(&drv->textconv, k, v);
+	if (!strcmp(type, "cachetextconv"))
+		return parse_bool(&drv->textconv_want_cache, k, v);
+	if (!strcmp(type, "wordregex"))
+		return git_config_string(&drv->word_regex, k, v);
+	if (!strcmp(type, "algorithm"))
+		return git_config_string(&drv->algorithm, k, v);
+
+	return 0;
+}
+
+struct userdiff_driver *userdiff_find_by_name(const char *name)
+{
+	int len = strlen(name);
+	struct userdiff_driver *driver = userdiff_find_by_namelen(name, len);
+	if (driver && driver->word_regex_multi_byte) {
+		if (regexec_supports_multi_byte_chars())
+			driver->word_regex = driver->word_regex_multi_byte;
+		driver->word_regex_multi_byte = NULL;
+	}
+	return driver;
+}
+
+struct userdiff_driver *userdiff_find_by_path(struct index_state *istate,
+					      const char *path)
+{
+	static struct attr_check *check;
+
+	if (!check)
+		check = attr_check_initl("diff", NULL);
+	if (!path)
+		return NULL;
+	git_check_attr(istate, path, check);
+
+	if (ATTR_TRUE(check->items[0].value))
+		return &driver_true;
+	if (ATTR_FALSE(check->items[0].value))
+		return &driver_false;
+	if (ATTR_UNSET(check->items[0].value))
+		return NULL;
+	return userdiff_find_by_name(check->items[0].value);
+}
+
+struct userdiff_driver *userdiff_get_textconv(struct repository *r,
+					      struct userdiff_driver *driver)
+{
+	if (!driver->textconv)
+		return NULL;
+
+	if (driver->textconv_want_cache && !driver->textconv_cache) {
+		struct notes_cache *c = xmalloc(sizeof(*c));
+		struct strbuf name = STRBUF_INIT;
+
+		strbuf_addf(&name, "textconv/%s", driver->name);
+		notes_cache_init(r, c, name.buf, driver->textconv);
+		driver->textconv_cache = c;
+		strbuf_release(&name);
+	}
+
+	return driver;
+}
+
+static int for_each_userdiff_driver_list(each_userdiff_driver_fn fn,
+					 enum userdiff_driver_type type, void *cb_data,
+					 struct userdiff_driver *drv,
+					 int drv_size)
+{
+	int i;
+	int ret;
+	for (i = 0; i < drv_size; i++) {
+		struct userdiff_driver *item = drv + i;
+		if ((ret = fn(item, type, cb_data)))
+			return ret;
+	}
+	return 0;
+}
+
+int for_each_userdiff_driver(each_userdiff_driver_fn fn, void *cb_data)
+{
+	int ret;
+
+	ret = for_each_userdiff_driver_list(fn, USERDIFF_DRIVER_TYPE_CUSTOM,
+					    cb_data, drivers, ndrivers);
+	if (ret)
+		return ret;
+
+	ret = for_each_userdiff_driver_list(fn, USERDIFF_DRIVER_TYPE_BUILTIN,
+					    cb_data, builtin_drivers,
+					    ARRAY_SIZE(builtin_drivers));
+	if (ret)
+		return ret;
+
+	return 0;
+}