Squashed 'third_party/git/' content from commit cb71568594

git-subtree-dir: third_party/git
git-subtree-split: cb715685942260375e1eb8153b0768a376e4ece7

1 files changed, 1971 insertions, 0 deletions

diff --git a/convert.c b/convert.c
new file mode 100644
index 000000000000..94ff83764922
--- /dev/null
+++ b/convert.c
@@ -0,0 +1,1971 @@
+#include "cache.h"
+#include "config.h"
+#include "object-store.h"
+#include "attr.h"
+#include "run-command.h"
+#include "quote.h"
+#include "sigchain.h"
+#include "pkt-line.h"
+#include "sub-process.h"
+#include "utf8.h"
+
+/*
+ * convert.c - convert a file when checking it out and checking it in.
+ *
+ * This should use the pathname to decide on whether it wants to do some
+ * more interesting conversions (automatic gzip/unzip, general format
+ * conversions etc etc), but by default it just does automatic CRLF<->LF
+ * translation when the "text" attribute or "auto_crlf" option is set.
+ */
+
+/* Stat bits: When BIN is set, the txt bits are unset */
+#define CONVERT_STAT_BITS_TXT_LF    0x1
+#define CONVERT_STAT_BITS_TXT_CRLF  0x2
+#define CONVERT_STAT_BITS_BIN       0x4
+
+enum crlf_action {
+	CRLF_UNDEFINED,
+	CRLF_BINARY,
+	CRLF_TEXT,
+	CRLF_TEXT_INPUT,
+	CRLF_TEXT_CRLF,
+	CRLF_AUTO,
+	CRLF_AUTO_INPUT,
+	CRLF_AUTO_CRLF
+};
+
+struct text_stat {
+	/* NUL, CR, LF and CRLF counts */
+	unsigned nul, lonecr, lonelf, crlf;
+
+	/* These are just approximations! */
+	unsigned printable, nonprintable;
+};
+
+static void gather_stats(const char *buf, unsigned long size, struct text_stat *stats)
+{
+	unsigned long i;
+
+	memset(stats, 0, sizeof(*stats));
+
+	for (i = 0; i < size; i++) {
+		unsigned char c = buf[i];
+		if (c == '\r') {
+			if (i+1 < size && buf[i+1] == '\n') {
+				stats->crlf++;
+				i++;
+			} else
+				stats->lonecr++;
+			continue;
+		}
+		if (c == '\n') {
+			stats->lonelf++;
+			continue;
+		}
+		if (c == 127)
+			/* DEL */
+			stats->nonprintable++;
+		else if (c < 32) {
+			switch (c) {
+				/* BS, HT, ESC and FF */
+			case '\b': case '\t': case '\033': case '\014':
+				stats->printable++;
+				break;
+			case 0:
+				stats->nul++;
+				/* fall through */
+			default:
+				stats->nonprintable++;
+			}
+		}
+		else
+			stats->printable++;
+	}
+
+	/* If file ends with EOF then don't count this EOF as non-printable. */
+	if (size >= 1 && buf[size-1] == '\032')
+		stats->nonprintable--;
+}
+
+/*
+ * The same heuristics as diff.c::mmfile_is_binary()
+ * We treat files with bare CR as binary
+ */
+static int convert_is_binary(const struct text_stat *stats)
+{
+	if (stats->lonecr)
+		return 1;
+	if (stats->nul)
+		return 1;
+	if ((stats->printable >> 7) < stats->nonprintable)
+		return 1;
+	return 0;
+}
+
+static unsigned int gather_convert_stats(const char *data, unsigned long size)
+{
+	struct text_stat stats;
+	int ret = 0;
+	if (!data || !size)
+		return 0;
+	gather_stats(data, size, &stats);
+	if (convert_is_binary(&stats))
+		ret |= CONVERT_STAT_BITS_BIN;
+	if (stats.crlf)
+		ret |= CONVERT_STAT_BITS_TXT_CRLF;
+	if (stats.lonelf)
+		ret |=  CONVERT_STAT_BITS_TXT_LF;
+
+	return ret;
+}
+
+static const char *gather_convert_stats_ascii(const char *data, unsigned long size)
+{
+	unsigned int convert_stats = gather_convert_stats(data, size);
+
+	if (convert_stats & CONVERT_STAT_BITS_BIN)
+		return "-text";
+	switch (convert_stats) {
+	case CONVERT_STAT_BITS_TXT_LF:
+		return "lf";
+	case CONVERT_STAT_BITS_TXT_CRLF:
+		return "crlf";
+	case CONVERT_STAT_BITS_TXT_LF | CONVERT_STAT_BITS_TXT_CRLF:
+		return "mixed";
+	default:
+		return "none";
+	}
+}
+
+const char *get_cached_convert_stats_ascii(const struct index_state *istate,
+					   const char *path)
+{
+	const char *ret;
+	unsigned long sz;
+	void *data = read_blob_data_from_index(istate, path, &sz);
+	ret = gather_convert_stats_ascii(data, sz);
+	free(data);
+	return ret;
+}
+
+const char *get_wt_convert_stats_ascii(const char *path)
+{
+	const char *ret = "";
+	struct strbuf sb = STRBUF_INIT;
+	if (strbuf_read_file(&sb, path, 0) >= 0)
+		ret = gather_convert_stats_ascii(sb.buf, sb.len);
+	strbuf_release(&sb);
+	return ret;
+}
+
+static int text_eol_is_crlf(void)
+{
+	if (auto_crlf == AUTO_CRLF_TRUE)
+		return 1;
+	else if (auto_crlf == AUTO_CRLF_INPUT)
+		return 0;
+	if (core_eol == EOL_CRLF)
+		return 1;
+	if (core_eol == EOL_UNSET && EOL_NATIVE == EOL_CRLF)
+		return 1;
+	return 0;
+}
+
+static enum eol output_eol(enum crlf_action crlf_action)
+{
+	switch (crlf_action) {
+	case CRLF_BINARY:
+		return EOL_UNSET;
+	case CRLF_TEXT_CRLF:
+		return EOL_CRLF;
+	case CRLF_TEXT_INPUT:
+		return EOL_LF;
+	case CRLF_UNDEFINED:
+	case CRLF_AUTO_CRLF:
+		return EOL_CRLF;
+	case CRLF_AUTO_INPUT:
+		return EOL_LF;
+	case CRLF_TEXT:
+	case CRLF_AUTO:
+		/* fall through */
+		return text_eol_is_crlf() ? EOL_CRLF : EOL_LF;
+	}
+	warning(_("illegal crlf_action %d"), (int)crlf_action);
+	return core_eol;
+}
+
+static void check_global_conv_flags_eol(const char *path, enum crlf_action crlf_action,
+			    struct text_stat *old_stats, struct text_stat *new_stats,
+			    int conv_flags)
+{
+	if (old_stats->crlf && !new_stats->crlf ) {
+		/*
+		 * CRLFs would not be restored by checkout
+		 */
+		if (conv_flags & CONV_EOL_RNDTRP_DIE)
+			die(_("CRLF would be replaced by LF in %s"), path);
+		else if (conv_flags & CONV_EOL_RNDTRP_WARN)
+			warning(_("CRLF will be replaced by LF in %s.\n"
+				  "The file will have its original line"
+				  " endings in your working directory"), path);
+	} else if (old_stats->lonelf && !new_stats->lonelf ) {
+		/*
+		 * CRLFs would be added by checkout
+		 */
+		if (conv_flags & CONV_EOL_RNDTRP_DIE)
+			die(_("LF would be replaced by CRLF in %s"), path);
+		else if (conv_flags & CONV_EOL_RNDTRP_WARN)
+			warning(_("LF will be replaced by CRLF in %s.\n"
+				  "The file will have its original line"
+				  " endings in your working directory"), path);
+	}
+}
+
+static int has_crlf_in_index(const struct index_state *istate, const char *path)
+{
+	unsigned long sz;
+	void *data;
+	const char *crp;
+	int has_crlf = 0;
+
+	data = read_blob_data_from_index(istate, path, &sz);
+	if (!data)
+		return 0;
+
+	crp = memchr(data, '\r', sz);
+	if (crp) {
+		unsigned int ret_stats;
+		ret_stats = gather_convert_stats(data, sz);
+		if (!(ret_stats & CONVERT_STAT_BITS_BIN) &&
+		    (ret_stats & CONVERT_STAT_BITS_TXT_CRLF))
+			has_crlf = 1;
+	}
+	free(data);
+	return has_crlf;
+}
+
+static int will_convert_lf_to_crlf(struct text_stat *stats,
+				   enum crlf_action crlf_action)
+{
+	if (output_eol(crlf_action) != EOL_CRLF)
+		return 0;
+	/* No "naked" LF? Nothing to convert, regardless. */
+	if (!stats->lonelf)
+		return 0;
+
+	if (crlf_action == CRLF_AUTO || crlf_action == CRLF_AUTO_INPUT || crlf_action == CRLF_AUTO_CRLF) {
+		/* If we have any CR or CRLF line endings, we do not touch it */
+		/* This is the new safer autocrlf-handling */
+		if (stats->lonecr || stats->crlf)
+			return 0;
+
+		if (convert_is_binary(stats))
+			return 0;
+	}
+	return 1;
+
+}
+
+static int validate_encoding(const char *path, const char *enc,
+		      const char *data, size_t len, int die_on_error)
+{
+	/* We only check for UTF here as UTF?? can be an alias for UTF-?? */
+	if (istarts_with(enc, "UTF")) {
+		/*
+		 * Check for detectable errors in UTF encodings
+		 */
+		if (has_prohibited_utf_bom(enc, data, len)) {
+			const char *error_msg = _(
+				"BOM is prohibited in '%s' if encoded as %s");
+			/*
+			 * This advice is shown for UTF-??BE and UTF-??LE encodings.
+			 * We cut off the last two characters of the encoding name
+			 * to generate the encoding name suitable for BOMs.
+			 */
+			const char *advise_msg = _(
+				"The file '%s' contains a byte order "
+				"mark (BOM). Please use UTF-%s as "
+				"working-tree-encoding.");
+			const char *stripped = NULL;
+			char *upper = xstrdup_toupper(enc);
+			upper[strlen(upper)-2] = '\0';
+			if (!skip_prefix(upper, "UTF-", &stripped))
+				skip_prefix(stripped, "UTF", &stripped);
+			advise(advise_msg, path, stripped);
+			free(upper);
+			if (die_on_error)
+				die(error_msg, path, enc);
+			else {
+				return error(error_msg, path, enc);
+			}
+
+		} else if (is_missing_required_utf_bom(enc, data, len)) {
+			const char *error_msg = _(
+				"BOM is required in '%s' if encoded as %s");
+			const char *advise_msg = _(
+				"The file '%s' is missing a byte order "
+				"mark (BOM). Please use UTF-%sBE or UTF-%sLE "
+				"(depending on the byte order) as "
+				"working-tree-encoding.");
+			const char *stripped = NULL;
+			char *upper = xstrdup_toupper(enc);
+			if (!skip_prefix(upper, "UTF-", &stripped))
+				skip_prefix(stripped, "UTF", &stripped);
+			advise(advise_msg, path, stripped, stripped);
+			free(upper);
+			if (die_on_error)
+				die(error_msg, path, enc);
+			else {
+				return error(error_msg, path, enc);
+			}
+		}
+
+	}
+	return 0;
+}
+
+static void trace_encoding(const char *context, const char *path,
+			   const char *encoding, const char *buf, size_t len)
+{
+	static struct trace_key coe = TRACE_KEY_INIT(WORKING_TREE_ENCODING);
+	struct strbuf trace = STRBUF_INIT;
+	int i;
+
+	strbuf_addf(&trace, "%s (%s, considered %s):\n", context, path, encoding);
+	for (i = 0; i < len && buf; ++i) {
+		strbuf_addf(
+			&trace, "| \033[2m%2i:\033[0m %2x \033[2m%c\033[0m%c",
+			i,
+			(unsigned char) buf[i],
+			(buf[i] > 32 && buf[i] < 127 ? buf[i] : ' '),
+			((i+1) % 8 && (i+1) < len ? ' ' : '\n')
+		);
+	}
+	strbuf_addchars(&trace, '\n', 1);
+
+	trace_strbuf(&coe, &trace);
+	strbuf_release(&trace);
+}
+
+static int check_roundtrip(const char *enc_name)
+{
+	/*
+	 * check_roundtrip_encoding contains a string of comma and/or
+	 * space separated encodings (eg. "UTF-16, ASCII, CP1125").
+	 * Search for the given encoding in that string.
+	 */
+	const char *found = strcasestr(check_roundtrip_encoding, enc_name);
+	const char *next;
+	int len;
+	if (!found)
+		return 0;
+	next = found + strlen(enc_name);
+	len = strlen(check_roundtrip_encoding);
+	return (found && (
+			/*
+			 * check that the found encoding is at the
+			 * beginning of check_roundtrip_encoding or
+			 * that it is prefixed with a space or comma
+			 */
+			found == check_roundtrip_encoding || (
+				(isspace(found[-1]) || found[-1] == ',')
+			)
+		) && (
+			/*
+			 * check that the found encoding is at the
+			 * end of check_roundtrip_encoding or
+			 * that it is suffixed with a space or comma
+			 */
+			next == check_roundtrip_encoding + len || (
+				next < check_roundtrip_encoding + len &&
+				(isspace(next[0]) || next[0] == ',')
+			)
+		));
+}
+
+static const char *default_encoding = "UTF-8";
+
+static int encode_to_git(const char *path, const char *src, size_t src_len,
+			 struct strbuf *buf, const char *enc, int conv_flags)
+{
+	char *dst;
+	size_t dst_len;
+	int die_on_error = conv_flags & CONV_WRITE_OBJECT;
+
+	/*
+	 * No encoding is specified or there is nothing to encode.
+	 * Tell the caller that the content was not modified.
+	 */
+	if (!enc || (src && !src_len))
+		return 0;
+
+	/*
+	 * Looks like we got called from "would_convert_to_git()".
+	 * This means Git wants to know if it would encode (= modify!)
+	 * the content. Let's answer with "yes", since an encoding was
+	 * specified.
+	 */
+	if (!buf && !src)
+		return 1;
+
+	if (validate_encoding(path, enc, src, src_len, die_on_error))
+		return 0;
+
+	trace_encoding("source", path, enc, src, src_len);
+	dst = reencode_string_len(src, src_len, default_encoding, enc,
+				  &dst_len);
+	if (!dst) {
+		/*
+		 * We could add the blob "as-is" to Git. However, on checkout
+		 * we would try to reencode to the original encoding. This
+		 * would fail and we would leave the user with a messed-up
+		 * working tree. Let's try to avoid this by screaming loud.
+		 */
+		const char* msg = _("failed to encode '%s' from %s to %s");
+		if (die_on_error)
+			die(msg, path, enc, default_encoding);
+		else {
+			error(msg, path, enc, default_encoding);
+			return 0;
+		}
+	}
+	trace_encoding("destination", path, default_encoding, dst, dst_len);
+
+	/*
+	 * UTF supports lossless conversion round tripping [1] and conversions
+	 * between UTF and other encodings are mostly round trip safe as
+	 * Unicode aims to be a superset of all other character encodings.
+	 * However, certain encodings (e.g. SHIFT-JIS) are known to have round
+	 * trip issues [2]. Check the round trip conversion for all encodings
+	 * listed in core.checkRoundtripEncoding.
+	 *
+	 * The round trip check is only performed if content is written to Git.
+	 * This ensures that no information is lost during conversion to/from
+	 * the internal UTF-8 representation.
+	 *
+	 * Please note, the code below is not tested because I was not able to
+	 * generate a faulty round trip without an iconv error. Iconv errors
+	 * are already caught above.
+	 *
+	 * [1] http://unicode.org/faq/utf_bom.html#gen2
+	 * [2] https://support.microsoft.com/en-us/help/170559/prb-conversion-problem-between-shift-jis-and-unicode
+	 */
+	if (die_on_error && check_roundtrip(enc)) {
+		char *re_src;
+		size_t re_src_len;
+
+		re_src = reencode_string_len(dst, dst_len,
+					     enc, default_encoding,
+					     &re_src_len);
+
+		trace_printf("Checking roundtrip encoding for %s...\n", enc);
+		trace_encoding("reencoded source", path, enc,
+			       re_src, re_src_len);
+
+		if (!re_src || src_len != re_src_len ||
+		    memcmp(src, re_src, src_len)) {
+			const char* msg = _("encoding '%s' from %s to %s and "
+					    "back is not the same");
+			die(msg, path, enc, default_encoding);
+		}
+
+		free(re_src);
+	}
+
+	strbuf_attach(buf, dst, dst_len, dst_len + 1);
+	return 1;
+}
+
+static int encode_to_worktree(const char *path, const char *src, size_t src_len,
+			      struct strbuf *buf, const char *enc)
+{
+	char *dst;
+	size_t dst_len;
+
+	/*
+	 * No encoding is specified or there is nothing to encode.
+	 * Tell the caller that the content was not modified.
+	 */
+	if (!enc || (src && !src_len))
+		return 0;
+
+	dst = reencode_string_len(src, src_len, enc, default_encoding,
+				  &dst_len);
+	if (!dst) {
+		error(_("failed to encode '%s' from %s to %s"),
+		      path, default_encoding, enc);
+		return 0;
+	}
+
+	strbuf_attach(buf, dst, dst_len, dst_len + 1);
+	return 1;
+}
+
+static int crlf_to_git(const struct index_state *istate,
+		       const char *path, const char *src, size_t len,
+		       struct strbuf *buf,
+		       enum crlf_action crlf_action, int conv_flags)
+{
+	struct text_stat stats;
+	char *dst;
+	int convert_crlf_into_lf;
+
+	if (crlf_action == CRLF_BINARY ||
+	    (src && !len))
+		return 0;
+
+	/*
+	 * If we are doing a dry-run and have no source buffer, there is
+	 * nothing to analyze; we must assume we would convert.
+	 */
+	if (!buf && !src)
+		return 1;
+
+	gather_stats(src, len, &stats);
+	/* Optimization: No CRLF? Nothing to convert, regardless. */
+	convert_crlf_into_lf = !!stats.crlf;
+
+	if (crlf_action == CRLF_AUTO || crlf_action == CRLF_AUTO_INPUT || crlf_action == CRLF_AUTO_CRLF) {
+		if (convert_is_binary(&stats))
+			return 0;
+		/*
+		 * If the file in the index has any CR in it, do not
+		 * convert.  This is the new safer autocrlf handling,
+		 * unless we want to renormalize in a merge or
+		 * cherry-pick.
+		 */
+		if ((!(conv_flags & CONV_EOL_RENORMALIZE)) &&
+		    has_crlf_in_index(istate, path))
+			convert_crlf_into_lf = 0;
+	}
+	if (((conv_flags & CONV_EOL_RNDTRP_WARN) ||
+	     ((conv_flags & CONV_EOL_RNDTRP_DIE) && len))) {
+		struct text_stat new_stats;
+		memcpy(&new_stats, &stats, sizeof(new_stats));
+		/* simulate "git add" */
+		if (convert_crlf_into_lf) {
+			new_stats.lonelf += new_stats.crlf;
+			new_stats.crlf = 0;
+		}
+		/* simulate "git checkout" */
+		if (will_convert_lf_to_crlf(&new_stats, crlf_action)) {
+			new_stats.crlf += new_stats.lonelf;
+			new_stats.lonelf = 0;
+		}
+		check_global_conv_flags_eol(path, crlf_action, &stats, &new_stats, conv_flags);
+	}
+	if (!convert_crlf_into_lf)
+		return 0;
+
+	/*
+	 * At this point all of our source analysis is done, and we are sure we
+	 * would convert. If we are in dry-run mode, we can give an answer.
+	 */
+	if (!buf)
+		return 1;
+
+	/* only grow if not in place */
+	if (strbuf_avail(buf) + buf->len < len)
+		strbuf_grow(buf, len - buf->len);
+	dst = buf->buf;
+	if (crlf_action == CRLF_AUTO || crlf_action == CRLF_AUTO_INPUT || crlf_action == CRLF_AUTO_CRLF) {
+		/*
+		 * If we guessed, we already know we rejected a file with
+		 * lone CR, and we can strip a CR without looking at what
+		 * follow it.
+		 */
+		do {
+			unsigned char c = *src++;
+			if (c != '\r')
+				*dst++ = c;
+		} while (--len);
+	} else {
+		do {
+			unsigned char c = *src++;
+			if (! (c == '\r' && (1 < len && *src == '\n')))
+				*dst++ = c;
+		} while (--len);
+	}
+	strbuf_setlen(buf, dst - buf->buf);
+	return 1;
+}
+
+static int crlf_to_worktree(const char *src, size_t len,
+			    struct strbuf *buf, enum crlf_action crlf_action)
+{
+	char *to_free = NULL;
+	struct text_stat stats;
+
+	if (!len || output_eol(crlf_action) != EOL_CRLF)
+		return 0;
+
+	gather_stats(src, len, &stats);
+	if (!will_convert_lf_to_crlf(&stats, crlf_action))
+		return 0;
+
+	/* are we "faking" in place editing ? */
+	if (src == buf->buf)
+		to_free = strbuf_detach(buf, NULL);
+
+	strbuf_grow(buf, len + stats.lonelf);
+	for (;;) {
+		const char *nl = memchr(src, '\n', len);
+		if (!nl)
+			break;
+		if (nl > src && nl[-1] == '\r') {
+			strbuf_add(buf, src, nl + 1 - src);
+		} else {
+			strbuf_add(buf, src, nl - src);
+			strbuf_addstr(buf, "\r\n");
+		}
+		len -= nl + 1 - src;
+		src  = nl + 1;
+	}
+	strbuf_add(buf, src, len);
+
+	free(to_free);
+	return 1;
+}
+
+struct filter_params {
+	const char *src;
+	unsigned long size;
+	int fd;
+	const char *cmd;
+	const char *path;
+};
+
+static int filter_buffer_or_fd(int in, int out, void *data)
+{
+	/*
+	 * Spawn cmd and feed the buffer contents through its stdin.
+	 */
+	struct child_process child_process = CHILD_PROCESS_INIT;
+	struct filter_params *params = (struct filter_params *)data;
+	int write_err, status;
+	const char *argv[] = { NULL, NULL };
+
+	/* apply % substitution to cmd */
+	struct strbuf cmd = STRBUF_INIT;
+	struct strbuf path = STRBUF_INIT;
+	struct strbuf_expand_dict_entry dict[] = {
+		{ "f", NULL, },
+		{ NULL, NULL, },
+	};
+
+	/* quote the path to preserve spaces, etc. */
+	sq_quote_buf(&path, params->path);
+	dict[0].value = path.buf;
+
+	/* expand all %f with the quoted path */
+	strbuf_expand(&cmd, params->cmd, strbuf_expand_dict_cb, &dict);
+	strbuf_release(&path);
+
+	argv[0] = cmd.buf;
+
+	child_process.argv = argv;
+	child_process.use_shell = 1;
+	child_process.in = -1;
+	child_process.out = out;
+
+	if (start_command(&child_process)) {
+		strbuf_release(&cmd);
+		return error(_("cannot fork to run external filter '%s'"),
+			     params->cmd);
+	}
+
+	sigchain_push(SIGPIPE, SIG_IGN);
+
+	if (params->src) {
+		write_err = (write_in_full(child_process.in,
+					   params->src, params->size) < 0);
+		if (errno == EPIPE)
+			write_err = 0;
+	} else {
+		write_err = copy_fd(params->fd, child_process.in);
+		if (write_err == COPY_WRITE_ERROR && errno == EPIPE)
+			write_err = 0;
+	}
+
+	if (close(child_process.in))
+		write_err = 1;
+	if (write_err)
+		error(_("cannot feed the input to external filter '%s'"),
+		      params->cmd);
+
+	sigchain_pop(SIGPIPE);
+
+	status = finish_command(&child_process);
+	if (status)
+		error(_("external filter '%s' failed %d"), params->cmd, status);
+
+	strbuf_release(&cmd);
+	return (write_err || status);
+}
+
+static int apply_single_file_filter(const char *path, const char *src, size_t len, int fd,
+				    struct strbuf *dst, const char *cmd)
+{
+	/*
+	 * Create a pipeline to have the command filter the buffer's
+	 * contents.
+	 *
+	 * (child --> cmd) --> us
+	 */
+	int err = 0;
+	struct strbuf nbuf = STRBUF_INIT;
+	struct async async;
+	struct filter_params params;
+
+	memset(&async, 0, sizeof(async));
+	async.proc = filter_buffer_or_fd;
+	async.data = &params;
+	async.out = -1;
+	params.src = src;
+	params.size = len;
+	params.fd = fd;
+	params.cmd = cmd;
+	params.path = path;
+
+	fflush(NULL);
+	if (start_async(&async))
+		return 0;	/* error was already reported */
+
+	if (strbuf_read(&nbuf, async.out, 0) < 0) {
+		err = error(_("read from external filter '%s' failed"), cmd);
+	}
+	if (close(async.out)) {
+		err = error(_("read from external filter '%s' failed"), cmd);
+	}
+	if (finish_async(&async)) {
+		err = error(_("external filter '%s' failed"), cmd);
+	}
+
+	if (!err) {
+		strbuf_swap(dst, &nbuf);
+	}
+	strbuf_release(&nbuf);
+	return !err;
+}
+
+#define CAP_CLEAN    (1u<<0)
+#define CAP_SMUDGE   (1u<<1)
+#define CAP_DELAY    (1u<<2)
+
+struct cmd2process {
+	struct subprocess_entry subprocess; /* must be the first member! */
+	unsigned int supported_capabilities;
+};
+
+static int subprocess_map_initialized;
+static struct hashmap subprocess_map;
+
+static int start_multi_file_filter_fn(struct subprocess_entry *subprocess)
+{
+	static int versions[] = {2, 0};
+	static struct subprocess_capability capabilities[] = {
+		{ "clean",  CAP_CLEAN  },
+		{ "smudge", CAP_SMUDGE },
+		{ "delay",  CAP_DELAY  },
+		{ NULL, 0 }
+	};
+	struct cmd2process *entry = (struct cmd2process *)subprocess;
+	return subprocess_handshake(subprocess, "git-filter", versions, NULL,
+				    capabilities,
+				    &entry->supported_capabilities);
+}
+
+static void handle_filter_error(const struct strbuf *filter_status,
+				struct cmd2process *entry,
+				const unsigned int wanted_capability)
+{
+	if (!strcmp(filter_status->buf, "error"))
+		; /* The filter signaled a problem with the file. */
+	else if (!strcmp(filter_status->buf, "abort") && wanted_capability) {
+		/*
+		 * The filter signaled a permanent problem. Don't try to filter
+		 * files with the same command for the lifetime of the current
+		 * Git process.
+		 */
+		 entry->supported_capabilities &= ~wanted_capability;
+	} else {
+		/*
+		 * Something went wrong with the protocol filter.
+		 * Force shutdown and restart if another blob requires filtering.
+		 */
+		error(_("external filter '%s' failed"), entry->subprocess.cmd);
+		subprocess_stop(&subprocess_map, &entry->subprocess);
+		free(entry);
+	}
+}
+
+static int apply_multi_file_filter(const char *path, const char *src, size_t len,
+				   int fd, struct strbuf *dst, const char *cmd,
+				   const unsigned int wanted_capability,
+				   struct delayed_checkout *dco)
+{
+	int err;
+	int can_delay = 0;
+	struct cmd2process *entry;
+	struct child_process *process;
+	struct strbuf nbuf = STRBUF_INIT;
+	struct strbuf filter_status = STRBUF_INIT;
+	const char *filter_type;
+
+	if (!subprocess_map_initialized) {
+		subprocess_map_initialized = 1;
+		hashmap_init(&subprocess_map, cmd2process_cmp, NULL, 0);
+		entry = NULL;
+	} else {
+		entry = (struct cmd2process *)subprocess_find_entry(&subprocess_map, cmd);
+	}
+
+	fflush(NULL);
+
+	if (!entry) {
+		entry = xmalloc(sizeof(*entry));
+		entry->supported_capabilities = 0;
+
+		if (subprocess_start(&subprocess_map, &entry->subprocess, cmd, start_multi_file_filter_fn)) {
+			free(entry);
+			return 0;
+		}
+	}
+	process = &entry->subprocess.process;
+
+	if (!(entry->supported_capabilities & wanted_capability))
+		return 0;
+
+	if (wanted_capability & CAP_CLEAN)
+		filter_type = "clean";
+	else if (wanted_capability & CAP_SMUDGE)
+		filter_type = "smudge";
+	else
+		die(_("unexpected filter type"));
+
+	sigchain_push(SIGPIPE, SIG_IGN);
+
+	assert(strlen(filter_type) < LARGE_PACKET_DATA_MAX - strlen("command=\n"));
+	err = packet_write_fmt_gently(process->in, "command=%s\n", filter_type);
+	if (err)
+		goto done;
+
+	err = strlen(path) > LARGE_PACKET_DATA_MAX - strlen("pathname=\n");
+	if (err) {
+		error(_("path name too long for external filter"));
+		goto done;
+	}
+
+	err = packet_write_fmt_gently(process->in, "pathname=%s\n", path);
+	if (err)
+		goto done;
+
+	if ((entry->supported_capabilities & CAP_DELAY) &&
+	    dco && dco->state == CE_CAN_DELAY) {
+		can_delay = 1;
+		err = packet_write_fmt_gently(process->in, "can-delay=1\n");
+		if (err)
+			goto done;
+	}
+
+	err = packet_flush_gently(process->in);
+	if (err)
+		goto done;
+
+	if (fd >= 0)
+		err = write_packetized_from_fd(fd, process->in);
+	else
+		err = write_packetized_from_buf(src, len, process->in);
+	if (err)
+		goto done;
+
+	err = subprocess_read_status(process->out, &filter_status);
+	if (err)
+		goto done;
+
+	if (can_delay && !strcmp(filter_status.buf, "delayed")) {
+		string_list_insert(&dco->filters, cmd);
+		string_list_insert(&dco->paths, path);
+	} else {
+		/* The filter got the blob and wants to send us a response. */
+		err = strcmp(filter_status.buf, "success");
+		if (err)
+			goto done;
+
+		err = read_packetized_to_strbuf(process->out, &nbuf) < 0;
+		if (err)
+			goto done;
+
+		err = subprocess_read_status(process->out, &filter_status);
+		if (err)
+			goto done;
+
+		err = strcmp(filter_status.buf, "success");
+	}
+
+done:
+	sigchain_pop(SIGPIPE);
+
+	if (err)
+		handle_filter_error(&filter_status, entry, wanted_capability);
+	else
+		strbuf_swap(dst, &nbuf);
+	strbuf_release(&nbuf);
+	return !err;
+}
+
+
+int async_query_available_blobs(const char *cmd, struct string_list *available_paths)
+{
+	int err;
+	char *line;
+	struct cmd2process *entry;
+	struct child_process *process;
+	struct strbuf filter_status = STRBUF_INIT;
+
+	assert(subprocess_map_initialized);
+	entry = (struct cmd2process *)subprocess_find_entry(&subprocess_map, cmd);
+	if (!entry) {
+		error(_("external filter '%s' is not available anymore although "
+			"not all paths have been filtered"), cmd);
+		return 0;
+	}
+	process = &entry->subprocess.process;
+	sigchain_push(SIGPIPE, SIG_IGN);
+
+	err = packet_write_fmt_gently(
+		process->in, "command=list_available_blobs\n");
+	if (err)
+		goto done;
+
+	err = packet_flush_gently(process->in);
+	if (err)
+		goto done;
+
+	while ((line = packet_read_line(process->out, NULL))) {
+		const char *path;
+		if (skip_prefix(line, "pathname=", &path))
+			string_list_insert(available_paths, xstrdup(path));
+		else
+			; /* ignore unknown keys */
+	}
+
+	err = subprocess_read_status(process->out, &filter_status);
+	if (err)
+		goto done;
+
+	err = strcmp(filter_status.buf, "success");
+
+done:
+	sigchain_pop(SIGPIPE);
+
+	if (err)
+		handle_filter_error(&filter_status, entry, 0);
+	return !err;
+}
+
+static struct convert_driver {
+	const char *name;
+	struct convert_driver *next;
+	const char *smudge;
+	const char *clean;
+	const char *process;
+	int required;
+} *user_convert, **user_convert_tail;
+
+static int apply_filter(const char *path, const char *src, size_t len,
+			int fd, struct strbuf *dst, struct convert_driver *drv,
+			const unsigned int wanted_capability,
+			struct delayed_checkout *dco)
+{
+	const char *cmd = NULL;
+
+	if (!drv)
+		return 0;
+
+	if (!dst)
+		return 1;
+
+	if ((wanted_capability & CAP_CLEAN) && !drv->process && drv->clean)
+		cmd = drv->clean;
+	else if ((wanted_capability & CAP_SMUDGE) && !drv->process && drv->smudge)
+		cmd = drv->smudge;
+
+	if (cmd && *cmd)
+		return apply_single_file_filter(path, src, len, fd, dst, cmd);
+	else if (drv->process && *drv->process)
+		return apply_multi_file_filter(path, src, len, fd, dst,
+			drv->process, wanted_capability, dco);
+
+	return 0;
+}
+
+static int read_convert_config(const char *var, const char *value, void *cb)
+{
+	const char *key, *name;
+	int namelen;
+	struct convert_driver *drv;
+
+	/*
+	 * External conversion drivers are configured using
+	 * "filter.<name>.variable".
+	 */
+	if (parse_config_key(var, "filter", &name, &namelen, &key) < 0 || !name)
+		return 0;
+	for (drv = user_convert; drv; drv = drv->next)
+		if (!strncmp(drv->name, name, namelen) && !drv->name[namelen])
+			break;
+	if (!drv) {
+		drv = xcalloc(1, sizeof(struct convert_driver));
+		drv->name = xmemdupz(name, namelen);
+		*user_convert_tail = drv;
+		user_convert_tail = &(drv->next);
+	}
+
+	/*
+	 * filter.<name>.smudge and filter.<name>.clean specifies
+	 * the command line:
+	 *
+	 *	command-line
+	 *
+	 * The command-line will not be interpolated in any way.
+	 */
+
+	if (!strcmp("smudge", key))
+		return git_config_string(&drv->smudge, var, value);
+
+	if (!strcmp("clean", key))
+		return git_config_string(&drv->clean, var, value);
+
+	if (!strcmp("process", key))
+		return git_config_string(&drv->process, var, value);
+
+	if (!strcmp("required", key)) {
+		drv->required = git_config_bool(var, value);
+		return 0;
+	}
+
+	return 0;
+}
+
+static int count_ident(const char *cp, unsigned long size)
+{
+	/*
+	 * "$Id: 0000000000000000000000000000000000000000 $" <=> "$Id$"
+	 */
+	int cnt = 0;
+	char ch;
+
+	while (size) {
+		ch = *cp++;
+		size--;
+		if (ch != '$')
+			continue;
+		if (size < 3)
+			break;
+		if (memcmp("Id", cp, 2))
+			continue;
+		ch = cp[2];
+		cp += 3;
+		size -= 3;
+		if (ch == '$')
+			cnt++; /* $Id$ */
+		if (ch != ':')
+			continue;
+
+		/*
+		 * "$Id: ... "; scan up to the closing dollar sign and discard.
+		 */
+		while (size) {
+			ch = *cp++;
+			size--;
+			if (ch == '$') {
+				cnt++;
+				break;
+			}
+			if (ch == '\n')
+				break;
+		}
+	}
+	return cnt;
+}
+
+static int ident_to_git(const char *src, size_t len,
+			struct strbuf *buf, int ident)
+{
+	char *dst, *dollar;
+
+	if (!ident || (src && !count_ident(src, len)))
+		return 0;
+
+	if (!buf)
+		return 1;
+
+	/* only grow if not in place */
+	if (strbuf_avail(buf) + buf->len < len)
+		strbuf_grow(buf, len - buf->len);
+	dst = buf->buf;
+	for (;;) {
+		dollar = memchr(src, '$', len);
+		if (!dollar)
+			break;
+		memmove(dst, src, dollar + 1 - src);
+		dst += dollar + 1 - src;
+		len -= dollar + 1 - src;
+		src  = dollar + 1;
+
+		if (len > 3 && !memcmp(src, "Id:", 3)) {
+			dollar = memchr(src + 3, '$', len - 3);
+			if (!dollar)
+				break;
+			if (memchr(src + 3, '\n', dollar - src - 3)) {
+				/* Line break before the next dollar. */
+				continue;
+			}
+
+			memcpy(dst, "Id$", 3);
+			dst += 3;
+			len -= dollar + 1 - src;
+			src  = dollar + 1;
+		}
+	}
+	memmove(dst, src, len);
+	strbuf_setlen(buf, dst + len - buf->buf);
+	return 1;
+}
+
+static int ident_to_worktree(const char *src, size_t len,
+			     struct strbuf *buf, int ident)
+{
+	struct object_id oid;
+	char *to_free = NULL, *dollar, *spc;
+	int cnt;
+
+	if (!ident)
+		return 0;
+
+	cnt = count_ident(src, len);
+	if (!cnt)
+		return 0;
+
+	/* are we "faking" in place editing ? */
+	if (src == buf->buf)
+		to_free = strbuf_detach(buf, NULL);
+	hash_object_file(src, len, "blob", &oid);
+
+	strbuf_grow(buf, len + cnt * (the_hash_algo->hexsz + 3));
+	for (;;) {
+		/* step 1: run to the next '$' */
+		dollar = memchr(src, '$', len);
+		if (!dollar)
+			break;
+		strbuf_add(buf, src, dollar + 1 - src);
+		len -= dollar + 1 - src;
+		src  = dollar + 1;
+
+		/* step 2: does it looks like a bit like Id:xxx$ or Id$ ? */
+		if (len < 3 || memcmp("Id", src, 2))
+			continue;
+
+		/* step 3: skip over Id$ or Id:xxxxx$ */
+		if (src[2] == '$') {
+			src += 3;
+			len -= 3;
+		} else if (src[2] == ':') {
+			/*
+			 * It's possible that an expanded Id has crept its way into the
+			 * repository, we cope with that by stripping the expansion out.
+			 * This is probably not a good idea, since it will cause changes
+			 * on checkout, which won't go away by stash, but let's keep it
+			 * for git-style ids.
+			 */
+			dollar = memchr(src + 3, '$', len - 3);
+			if (!dollar) {
+				/* incomplete keyword, no more '$', so just quit the loop */
+				break;
+			}
+
+			if (memchr(src + 3, '\n', dollar - src - 3)) {
+				/* Line break before the next dollar. */
+				continue;
+			}
+
+			spc = memchr(src + 4, ' ', dollar - src - 4);
+			if (spc && spc < dollar-1) {
+				/* There are spaces in unexpected places.
+				 * This is probably an id from some other
+				 * versioning system. Keep it for now.
+				 */
+				continue;
+			}
+
+			len -= dollar + 1 - src;
+			src  = dollar + 1;
+		} else {
+			/* it wasn't a "Id$" or "Id:xxxx$" */
+			continue;
+		}
+
+		/* step 4: substitute */
+		strbuf_addstr(buf, "Id: ");
+		strbuf_addstr(buf, oid_to_hex(&oid));
+		strbuf_addstr(buf, " $");
+	}
+	strbuf_add(buf, src, len);
+
+	free(to_free);
+	return 1;
+}
+
+static const char *git_path_check_encoding(struct attr_check_item *check)
+{
+	const char *value = check->value;
+
+	if (ATTR_UNSET(value) || !strlen(value))
+		return NULL;
+
+	if (ATTR_TRUE(value) || ATTR_FALSE(value)) {
+		die(_("true/false are no valid working-tree-encodings"));
+	}
+
+	/* Don't encode to the default encoding */
+	if (same_encoding(value, default_encoding))
+		return NULL;
+
+	return value;
+}
+
+static enum crlf_action git_path_check_crlf(struct attr_check_item *check)
+{
+	const char *value = check->value;
+
+	if (ATTR_TRUE(value))
+		return CRLF_TEXT;
+	else if (ATTR_FALSE(value))
+		return CRLF_BINARY;
+	else if (ATTR_UNSET(value))
+		;
+	else if (!strcmp(value, "input"))
+		return CRLF_TEXT_INPUT;
+	else if (!strcmp(value, "auto"))
+		return CRLF_AUTO;
+	return CRLF_UNDEFINED;
+}
+
+static enum eol git_path_check_eol(struct attr_check_item *check)
+{
+	const char *value = check->value;
+
+	if (ATTR_UNSET(value))
+		;
+	else if (!strcmp(value, "lf"))
+		return EOL_LF;
+	else if (!strcmp(value, "crlf"))
+		return EOL_CRLF;
+	return EOL_UNSET;
+}
+
+static struct convert_driver *git_path_check_convert(struct attr_check_item *check)
+{
+	const char *value = check->value;
+	struct convert_driver *drv;
+
+	if (ATTR_TRUE(value) || ATTR_FALSE(value) || ATTR_UNSET(value))
+		return NULL;
+	for (drv = user_convert; drv; drv = drv->next)
+		if (!strcmp(value, drv->name))
+			return drv;
+	return NULL;
+}
+
+static int git_path_check_ident(struct attr_check_item *check)
+{
+	const char *value = check->value;
+
+	return !!ATTR_TRUE(value);
+}
+
+struct conv_attrs {
+	struct convert_driver *drv;
+	enum crlf_action attr_action; /* What attr says */
+	enum crlf_action crlf_action; /* When no attr is set, use core.autocrlf */
+	int ident;
+	const char *working_tree_encoding; /* Supported encoding or default encoding if NULL */
+};
+
+static void convert_attrs(const struct index_state *istate,
+			  struct conv_attrs *ca, const char *path)
+{
+	static struct attr_check *check;
+	struct attr_check_item *ccheck = NULL;
+
+	if (!check) {
+		check = attr_check_initl("crlf", "ident", "filter",
+					 "eol", "text", "working-tree-encoding",
+					 NULL);
+		user_convert_tail = &user_convert;
+		git_config(read_convert_config, NULL);
+	}
+
+	git_check_attr(istate, path, check);
+	ccheck = check->items;
+	ca->crlf_action = git_path_check_crlf(ccheck + 4);
+	if (ca->crlf_action == CRLF_UNDEFINED)
+		ca->crlf_action = git_path_check_crlf(ccheck + 0);
+	ca->ident = git_path_check_ident(ccheck + 1);
+	ca->drv = git_path_check_convert(ccheck + 2);
+	if (ca->crlf_action != CRLF_BINARY) {
+		enum eol eol_attr = git_path_check_eol(ccheck + 3);
+		if (ca->crlf_action == CRLF_AUTO && eol_attr == EOL_LF)
+			ca->crlf_action = CRLF_AUTO_INPUT;
+		else if (ca->crlf_action == CRLF_AUTO && eol_attr == EOL_CRLF)
+			ca->crlf_action = CRLF_AUTO_CRLF;
+		else if (eol_attr == EOL_LF)
+			ca->crlf_action = CRLF_TEXT_INPUT;
+		else if (eol_attr == EOL_CRLF)
+			ca->crlf_action = CRLF_TEXT_CRLF;
+	}
+	ca->working_tree_encoding = git_path_check_encoding(ccheck + 5);
+
+	/* Save attr and make a decision for action */
+	ca->attr_action = ca->crlf_action;
+	if (ca->crlf_action == CRLF_TEXT)
+		ca->crlf_action = text_eol_is_crlf() ? CRLF_TEXT_CRLF : CRLF_TEXT_INPUT;
+	if (ca->crlf_action == CRLF_UNDEFINED && auto_crlf == AUTO_CRLF_FALSE)
+		ca->crlf_action = CRLF_BINARY;
+	if (ca->crlf_action == CRLF_UNDEFINED && auto_crlf == AUTO_CRLF_TRUE)
+		ca->crlf_action = CRLF_AUTO_CRLF;
+	if (ca->crlf_action == CRLF_UNDEFINED && auto_crlf == AUTO_CRLF_INPUT)
+		ca->crlf_action = CRLF_AUTO_INPUT;
+}
+
+int would_convert_to_git_filter_fd(const struct index_state *istate, const char *path)
+{
+	struct conv_attrs ca;
+
+	convert_attrs(istate, &ca, path);
+	if (!ca.drv)
+		return 0;
+
+	/*
+	 * Apply a filter to an fd only if the filter is required to succeed.
+	 * We must die if the filter fails, because the original data before
+	 * filtering is not available.
+	 */
+	if (!ca.drv->required)
+		return 0;
+
+	return apply_filter(path, NULL, 0, -1, NULL, ca.drv, CAP_CLEAN, NULL);
+}
+
+const char *get_convert_attr_ascii(const struct index_state *istate, const char *path)
+{
+	struct conv_attrs ca;
+
+	convert_attrs(istate, &ca, path);
+	switch (ca.attr_action) {
+	case CRLF_UNDEFINED:
+		return "";
+	case CRLF_BINARY:
+		return "-text";
+	case CRLF_TEXT:
+		return "text";
+	case CRLF_TEXT_INPUT:
+		return "text eol=lf";
+	case CRLF_TEXT_CRLF:
+		return "text eol=crlf";
+	case CRLF_AUTO:
+		return "text=auto";
+	case CRLF_AUTO_CRLF:
+		return "text=auto eol=crlf";
+	case CRLF_AUTO_INPUT:
+		return "text=auto eol=lf";
+	}
+	return "";
+}
+
+int convert_to_git(const struct index_state *istate,
+		   const char *path, const char *src, size_t len,
+		   struct strbuf *dst, int conv_flags)
+{
+	int ret = 0;
+	struct conv_attrs ca;
+
+	convert_attrs(istate, &ca, path);
+
+	ret |= apply_filter(path, src, len, -1, dst, ca.drv, CAP_CLEAN, NULL);
+	if (!ret && ca.drv && ca.drv->required)
+		die(_("%s: clean filter '%s' failed"), path, ca.drv->name);
+
+	if (ret && dst) {
+		src = dst->buf;
+		len = dst->len;
+	}
+
+	ret |= encode_to_git(path, src, len, dst, ca.working_tree_encoding, conv_flags);
+	if (ret && dst) {
+		src = dst->buf;
+		len = dst->len;
+	}
+
+	if (!(conv_flags & CONV_EOL_KEEP_CRLF)) {
+		ret |= crlf_to_git(istate, path, src, len, dst, ca.crlf_action, conv_flags);
+		if (ret && dst) {
+			src = dst->buf;
+			len = dst->len;
+		}
+	}
+	return ret | ident_to_git(src, len, dst, ca.ident);
+}
+
+void convert_to_git_filter_fd(const struct index_state *istate,
+			      const char *path, int fd, struct strbuf *dst,
+			      int conv_flags)
+{
+	struct conv_attrs ca;
+	convert_attrs(istate, &ca, path);
+
+	assert(ca.drv);
+	assert(ca.drv->clean || ca.drv->process);
+
+	if (!apply_filter(path, NULL, 0, fd, dst, ca.drv, CAP_CLEAN, NULL))
+		die(_("%s: clean filter '%s' failed"), path, ca.drv->name);
+
+	encode_to_git(path, dst->buf, dst->len, dst, ca.working_tree_encoding, conv_flags);
+	crlf_to_git(istate, path, dst->buf, dst->len, dst, ca.crlf_action, conv_flags);
+	ident_to_git(dst->buf, dst->len, dst, ca.ident);
+}
+
+static int convert_to_working_tree_internal(const struct index_state *istate,
+					    const char *path, const char *src,
+					    size_t len, struct strbuf *dst,
+					    int normalizing, struct delayed_checkout *dco)
+{
+	int ret = 0, ret_filter = 0;
+	struct conv_attrs ca;
+
+	convert_attrs(istate, &ca, path);
+
+	ret |= ident_to_worktree(src, len, dst, ca.ident);
+	if (ret) {
+		src = dst->buf;
+		len = dst->len;
+	}
+	/*
+	 * CRLF conversion can be skipped if normalizing, unless there
+	 * is a smudge or process filter (even if the process filter doesn't
+	 * support smudge).  The filters might expect CRLFs.
+	 */
+	if ((ca.drv && (ca.drv->smudge || ca.drv->process)) || !normalizing) {
+		ret |= crlf_to_worktree(src, len, dst, ca.crlf_action);
+		if (ret) {
+			src = dst->buf;
+			len = dst->len;
+		}
+	}
+
+	ret |= encode_to_worktree(path, src, len, dst, ca.working_tree_encoding);
+	if (ret) {
+		src = dst->buf;
+		len = dst->len;
+	}
+
+	ret_filter = apply_filter(
+		path, src, len, -1, dst, ca.drv, CAP_SMUDGE, dco);
+	if (!ret_filter && ca.drv && ca.drv->required)
+		die(_("%s: smudge filter %s failed"), path, ca.drv->name);
+
+	return ret | ret_filter;
+}
+
+int async_convert_to_working_tree(const struct index_state *istate,
+				  const char *path, const char *src,
+				  size_t len, struct strbuf *dst,
+				  void *dco)
+{
+	return convert_to_working_tree_internal(istate, path, src, len, dst, 0, dco);
+}
+
+int convert_to_working_tree(const struct index_state *istate,
+			    const char *path, const char *src,
+			    size_t len, struct strbuf *dst)
+{
+	return convert_to_working_tree_internal(istate, path, src, len, dst, 0, NULL);
+}
+
+int renormalize_buffer(const struct index_state *istate, const char *path,
+		       const char *src, size_t len, struct strbuf *dst)
+{
+	int ret = convert_to_working_tree_internal(istate, path, src, len, dst, 1, NULL);
+	if (ret) {
+		src = dst->buf;
+		len = dst->len;
+	}
+	return ret | convert_to_git(istate, path, src, len, dst, CONV_EOL_RENORMALIZE);
+}
+
+/*****************************************************************
+ *
+ * Streaming conversion support
+ *
+ *****************************************************************/
+
+typedef int (*filter_fn)(struct stream_filter *,
+			 const char *input, size_t *isize_p,
+			 char *output, size_t *osize_p);
+typedef void (*free_fn)(struct stream_filter *);
+
+struct stream_filter_vtbl {
+	filter_fn filter;
+	free_fn free;
+};
+
+struct stream_filter {
+	struct stream_filter_vtbl *vtbl;
+};
+
+static int null_filter_fn(struct stream_filter *filter,
+			  const char *input, size_t *isize_p,
+			  char *output, size_t *osize_p)
+{
+	size_t count;
+
+	if (!input)
+		return 0; /* we do not keep any states */
+	count = *isize_p;
+	if (*osize_p < count)
+		count = *osize_p;
+	if (count) {
+		memmove(output, input, count);
+		*isize_p -= count;
+		*osize_p -= count;
+	}
+	return 0;
+}
+
+static void null_free_fn(struct stream_filter *filter)
+{
+	; /* nothing -- null instances are shared */
+}
+
+static struct stream_filter_vtbl null_vtbl = {
+	null_filter_fn,
+	null_free_fn,
+};
+
+static struct stream_filter null_filter_singleton = {
+	&null_vtbl,
+};
+
+int is_null_stream_filter(struct stream_filter *filter)
+{
+	return filter == &null_filter_singleton;
+}
+
+
+/*
+ * LF-to-CRLF filter
+ */
+
+struct lf_to_crlf_filter {
+	struct stream_filter filter;
+	unsigned has_held:1;
+	char held;
+};
+
+static int lf_to_crlf_filter_fn(struct stream_filter *filter,
+				const char *input, size_t *isize_p,
+				char *output, size_t *osize_p)
+{
+	size_t count, o = 0;
+	struct lf_to_crlf_filter *lf_to_crlf = (struct lf_to_crlf_filter *)filter;
+
+	/*
+	 * We may be holding onto the CR to see if it is followed by a
+	 * LF, in which case we would need to go to the main loop.
+	 * Otherwise, just emit it to the output stream.
+	 */
+	if (lf_to_crlf->has_held && (lf_to_crlf->held != '\r' || !input)) {
+		output[o++] = lf_to_crlf->held;
+		lf_to_crlf->has_held = 0;
+	}
+
+	/* We are told to drain */
+	if (!input) {
+		*osize_p -= o;
+		return 0;
+	}
+
+	count = *isize_p;
+	if (count || lf_to_crlf->has_held) {
+		size_t i;
+		int was_cr = 0;
+
+		if (lf_to_crlf->has_held) {
+			was_cr = 1;
+			lf_to_crlf->has_held = 0;
+		}
+
+		for (i = 0; o < *osize_p && i < count; i++) {
+			char ch = input[i];
+
+			if (ch == '\n') {
+				output[o++] = '\r';
+			} else if (was_cr) {
+				/*
+				 * Previous round saw CR and it is not followed
+				 * by a LF; emit the CR before processing the
+				 * current character.
+				 */
+				output[o++] = '\r';
+			}
+
+			/*
+			 * We may have consumed the last output slot,
+			 * in which case we need to break out of this
+			 * loop; hold the current character before
+			 * returning.
+			 */
+			if (*osize_p <= o) {
+				lf_to_crlf->has_held = 1;
+				lf_to_crlf->held = ch;
+				continue; /* break but increment i */
+			}
+
+			if (ch == '\r') {
+				was_cr = 1;
+				continue;
+			}
+
+			was_cr = 0;
+			output[o++] = ch;
+		}
+
+		*osize_p -= o;
+		*isize_p -= i;
+
+		if (!lf_to_crlf->has_held && was_cr) {
+			lf_to_crlf->has_held = 1;
+			lf_to_crlf->held = '\r';
+		}
+	}
+	return 0;
+}
+
+static void lf_to_crlf_free_fn(struct stream_filter *filter)
+{
+	free(filter);
+}
+
+static struct stream_filter_vtbl lf_to_crlf_vtbl = {
+	lf_to_crlf_filter_fn,
+	lf_to_crlf_free_fn,
+};
+
+static struct stream_filter *lf_to_crlf_filter(void)
+{
+	struct lf_to_crlf_filter *lf_to_crlf = xcalloc(1, sizeof(*lf_to_crlf));
+
+	lf_to_crlf->filter.vtbl = &lf_to_crlf_vtbl;
+	return (struct stream_filter *)lf_to_crlf;
+}
+
+/*
+ * Cascade filter
+ */
+#define FILTER_BUFFER 1024
+struct cascade_filter {
+	struct stream_filter filter;
+	struct stream_filter *one;
+	struct stream_filter *two;
+	char buf[FILTER_BUFFER];
+	int end, ptr;
+};
+
+static int cascade_filter_fn(struct stream_filter *filter,
+			     const char *input, size_t *isize_p,
+			     char *output, size_t *osize_p)
+{
+	struct cascade_filter *cas = (struct cascade_filter *) filter;
+	size_t filled = 0;
+	size_t sz = *osize_p;
+	size_t to_feed, remaining;
+
+	/*
+	 * input -- (one) --> buf -- (two) --> output
+	 */
+	while (filled < sz) {
+		remaining = sz - filled;
+
+		/* do we already have something to feed two with? */
+		if (cas->ptr < cas->end) {
+			to_feed = cas->end - cas->ptr;
+			if (stream_filter(cas->two,
+					  cas->buf + cas->ptr, &to_feed,
+					  output + filled, &remaining))
+				return -1;
+			cas->ptr += (cas->end - cas->ptr) - to_feed;
+			filled = sz - remaining;
+			continue;
+		}
+
+		/* feed one from upstream and have it emit into our buffer */
+		to_feed = input ? *isize_p : 0;
+		if (input && !to_feed)
+			break;
+		remaining = sizeof(cas->buf);
+		if (stream_filter(cas->one,
+				  input, &to_feed,
+				  cas->buf, &remaining))
+			return -1;
+		cas->end = sizeof(cas->buf) - remaining;
+		cas->ptr = 0;
+		if (input) {
+			size_t fed = *isize_p - to_feed;
+			*isize_p -= fed;
+			input += fed;
+		}
+
+		/* do we know that we drained one completely? */
+		if (input || cas->end)
+			continue;
+
+		/* tell two to drain; we have nothing more to give it */
+		to_feed = 0;
+		remaining = sz - filled;
+		if (stream_filter(cas->two,
+				  NULL, &to_feed,
+				  output + filled, &remaining))
+			return -1;
+		if (remaining == (sz - filled))
+			break; /* completely drained two */
+		filled = sz - remaining;
+	}
+	*osize_p -= filled;
+	return 0;
+}
+
+static void cascade_free_fn(struct stream_filter *filter)
+{
+	struct cascade_filter *cas = (struct cascade_filter *)filter;
+	free_stream_filter(cas->one);
+	free_stream_filter(cas->two);
+	free(filter);
+}
+
+static struct stream_filter_vtbl cascade_vtbl = {
+	cascade_filter_fn,
+	cascade_free_fn,
+};
+
+static struct stream_filter *cascade_filter(struct stream_filter *one,
+					    struct stream_filter *two)
+{
+	struct cascade_filter *cascade;
+
+	if (!one || is_null_stream_filter(one))
+		return two;
+	if (!two || is_null_stream_filter(two))
+		return one;
+
+	cascade = xmalloc(sizeof(*cascade));
+	cascade->one = one;
+	cascade->two = two;
+	cascade->end = cascade->ptr = 0;
+	cascade->filter.vtbl = &cascade_vtbl;
+	return (struct stream_filter *)cascade;
+}
+
+/*
+ * ident filter
+ */
+#define IDENT_DRAINING (-1)
+#define IDENT_SKIPPING (-2)
+struct ident_filter {
+	struct stream_filter filter;
+	struct strbuf left;
+	int state;
+	char ident[GIT_MAX_HEXSZ + 5]; /* ": x40 $" */
+};
+
+static int is_foreign_ident(const char *str)
+{
+	int i;
+
+	if (!skip_prefix(str, "$Id: ", &str))
+		return 0;
+	for (i = 0; str[i]; i++) {
+		if (isspace(str[i]) && str[i+1] != '$')
+			return 1;
+	}
+	return 0;
+}
+
+static void ident_drain(struct ident_filter *ident, char **output_p, size_t *osize_p)
+{
+	size_t to_drain = ident->left.len;
+
+	if (*osize_p < to_drain)
+		to_drain = *osize_p;
+	if (to_drain) {
+		memcpy(*output_p, ident->left.buf, to_drain);
+		strbuf_remove(&ident->left, 0, to_drain);
+		*output_p += to_drain;
+		*osize_p -= to_drain;
+	}
+	if (!ident->left.len)
+		ident->state = 0;
+}
+
+static int ident_filter_fn(struct stream_filter *filter,
+			   const char *input, size_t *isize_p,
+			   char *output, size_t *osize_p)
+{
+	struct ident_filter *ident = (struct ident_filter *)filter;
+	static const char head[] = "$Id";
+
+	if (!input) {
+		/* drain upon eof */
+		switch (ident->state) {
+		default:
+			strbuf_add(&ident->left, head, ident->state);
+			/* fallthrough */
+		case IDENT_SKIPPING:
+			/* fallthrough */
+		case IDENT_DRAINING:
+			ident_drain(ident, &output, osize_p);
+		}
+		return 0;
+	}
+
+	while (*isize_p || (ident->state == IDENT_DRAINING)) {
+		int ch;
+
+		if (ident->state == IDENT_DRAINING) {
+			ident_drain(ident, &output, osize_p);
+			if (!*osize_p)
+				break;
+			continue;
+		}
+
+		ch = *(input++);
+		(*isize_p)--;
+
+		if (ident->state == IDENT_SKIPPING) {
+			/*
+			 * Skipping until '$' or LF, but keeping them
+			 * in case it is a foreign ident.
+			 */
+			strbuf_addch(&ident->left, ch);
+			if (ch != '\n' && ch != '$')
+				continue;
+			if (ch == '$' && !is_foreign_ident(ident->left.buf)) {
+				strbuf_setlen(&ident->left, sizeof(head) - 1);
+				strbuf_addstr(&ident->left, ident->ident);
+			}
+			ident->state = IDENT_DRAINING;
+			continue;
+		}
+
+		if (ident->state < sizeof(head) &&
+		    head[ident->state] == ch) {
+			ident->state++;
+			continue;
+		}
+
+		if (ident->state)
+			strbuf_add(&ident->left, head, ident->state);
+		if (ident->state == sizeof(head) - 1) {
+			if (ch != ':' && ch != '$') {
+				strbuf_addch(&ident->left, ch);
+				ident->state = 0;
+				continue;
+			}
+
+			if (ch == ':') {
+				strbuf_addch(&ident->left, ch);
+				ident->state = IDENT_SKIPPING;
+			} else {
+				strbuf_addstr(&ident->left, ident->ident);
+				ident->state = IDENT_DRAINING;
+			}
+			continue;
+		}
+
+		strbuf_addch(&ident->left, ch);
+		ident->state = IDENT_DRAINING;
+	}
+	return 0;
+}
+
+static void ident_free_fn(struct stream_filter *filter)
+{
+	struct ident_filter *ident = (struct ident_filter *)filter;
+	strbuf_release(&ident->left);
+	free(filter);
+}
+
+static struct stream_filter_vtbl ident_vtbl = {
+	ident_filter_fn,
+	ident_free_fn,
+};
+
+static struct stream_filter *ident_filter(const struct object_id *oid)
+{
+	struct ident_filter *ident = xmalloc(sizeof(*ident));
+
+	xsnprintf(ident->ident, sizeof(ident->ident),
+		  ": %s $", oid_to_hex(oid));
+	strbuf_init(&ident->left, 0);
+	ident->filter.vtbl = &ident_vtbl;
+	ident->state = 0;
+	return (struct stream_filter *)ident;
+}
+
+/*
+ * Return an appropriately constructed filter for the path, or NULL if
+ * the contents cannot be filtered without reading the whole thing
+ * in-core.
+ *
+ * Note that you would be crazy to set CRLF, smuge/clean or ident to a
+ * large binary blob you would want us not to slurp into the memory!
+ */
+struct stream_filter *get_stream_filter(const struct index_state *istate,
+					const char *path,
+					const struct object_id *oid)
+{
+	struct conv_attrs ca;
+	struct stream_filter *filter = NULL;
+
+	convert_attrs(istate, &ca, path);
+	if (ca.drv && (ca.drv->process || ca.drv->smudge || ca.drv->clean))
+		return NULL;
+
+	if (ca.working_tree_encoding)
+		return NULL;
+
+	if (ca.crlf_action == CRLF_AUTO || ca.crlf_action == CRLF_AUTO_CRLF)
+		return NULL;
+
+	if (ca.ident)
+		filter = ident_filter(oid);
+
+	if (output_eol(ca.crlf_action) == EOL_CRLF)
+		filter = cascade_filter(filter, lf_to_crlf_filter());
+	else
+		filter = cascade_filter(filter, &null_filter_singleton);
+
+	return filter;
+}
+
+void free_stream_filter(struct stream_filter *filter)
+{
+	filter->vtbl->free(filter);
+}
+
+int stream_filter(struct stream_filter *filter,
+		  const char *input, size_t *isize_p,
+		  char *output, size_t *osize_p)
+{
+	return filter->vtbl->filter(filter, input, isize_p, output, osize_p);
+}