diff.c: Output the text graph padding before each diff line
[gitweb.git] / diff.c
diff --git a/diff.c b/diff.c
index 494f5601e97e7395e647296bc7f8090331a47c43..7f2538d3390313719b27806b273d215ef720be00 100644 (file)
--- a/diff.c
+++ b/diff.c
@@ -194,8 +194,8 @@ struct emit_callback {
        sane_truncate_fn truncate;
        const char **label_path;
        struct diff_words_data *diff_words;
+       struct diff_options *opt;
        int *found_changesp;
-       FILE *file;
        struct strbuf *header;
 };
 
@@ -282,11 +282,19 @@ static void check_blank_at_eof(mmfile_t *mf1, mmfile_t *mf2,
        ecbdata->blank_at_eof_in_postimage = (at - l2) + 1;
 }
 
-static void emit_line_0(FILE *file, const char *set, const char *reset,
+static void emit_line_0(struct diff_options *o, const char *set, const char *reset,
                        int first, const char *line, int len)
 {
        int has_trailing_newline, has_trailing_carriage_return;
        int nofirst;
+       FILE *file = o->file;
+
+       if (o->output_prefix) {
+               struct strbuf *msg = NULL;
+               msg = o->output_prefix(o, o->output_prefix_data);
+               assert(msg);
+               fwrite(msg->buf, msg->len, 1, file);
+       }
 
        if (len == 0) {
                has_trailing_newline = (first == '\n');
@@ -316,10 +324,10 @@ static void emit_line_0(FILE *file, const char *set, const char *reset,
                fputc('\n', file);
 }
 
-static void emit_line(FILE *file, const char *set, const char *reset,
+static void emit_line(struct diff_options *o, const char *set, const char *reset,
                      const char *line, int len)
 {
-       emit_line_0(file, set, reset, line[0], line+1, len-1);
+       emit_line_0(o, set, reset, line[0], line+1, len-1);
 }
 
 static int new_blank_line_at_eof(struct emit_callback *ecbdata, const char *line, int len)
@@ -341,15 +349,15 @@ static void emit_add_line(const char *reset,
        const char *set = diff_get_color(ecbdata->color_diff, DIFF_FILE_NEW);
 
        if (!*ws)
-               emit_line_0(ecbdata->file, set, reset, '+', line, len);
+               emit_line_0(ecbdata->opt, set, reset, '+', line, len);
        else if (new_blank_line_at_eof(ecbdata, line, len))
                /* Blank line at EOF - paint '+' as well */
-               emit_line_0(ecbdata->file, ws, reset, '+', line, len);
+               emit_line_0(ecbdata->opt, ws, reset, '+', line, len);
        else {
                /* Emit just the prefix, then the rest. */
-               emit_line_0(ecbdata->file, set, reset, '+', "", 0);
+               emit_line_0(ecbdata->opt, set, reset, '+', "", 0);
                ws_check_emit(line, len, ecbdata->ws_rule,
-                             ecbdata->file, set, reset, ws);
+                             ecbdata->opt->file, set, reset, ws);
        }
 }
 
@@ -370,23 +378,23 @@ static void emit_hunk_header(struct emit_callback *ecbdata,
        if (len < 10 ||
            memcmp(line, atat, 2) ||
            !(ep = memmem(line + 2, len - 2, atat, 2))) {
-               emit_line(ecbdata->file, plain, reset, line, len);
+               emit_line(ecbdata->opt, plain, reset, line, len);
                return;
        }
        ep += 2; /* skip over @@ */
 
        /* The hunk header in fraginfo color */
-       emit_line(ecbdata->file, frag, reset, line, ep - line);
+       emit_line(ecbdata->opt, frag, reset, line, ep - line);
 
        /* blank before the func header */
        for (cp = ep; ep - line < len; ep++)
                if (*ep != ' ' && *ep != '\t')
                        break;
        if (ep != cp)
-               emit_line(ecbdata->file, plain, reset, cp, ep - cp);
+               emit_line(ecbdata->opt, plain, reset, cp, ep - cp);
 
        if (ep < line + len)
-               emit_line(ecbdata->file, func, reset, ep, line + len - ep);
+               emit_line(ecbdata->opt, func, reset, ep, line + len - ep);
 }
 
 static struct diff_tempfile *claim_diff_tempfile(void) {
@@ -446,7 +454,7 @@ static void emit_rewrite_lines(struct emit_callback *ecb,
                len = endp ? (endp - data + 1) : size;
                if (prefix != '+') {
                        ecb->lno_in_preimage++;
-                       emit_line_0(ecb->file, old, reset, '-',
+                       emit_line_0(ecb->opt, old, reset, '-',
                                    data, len);
                } else {
                        ecb->lno_in_postimage++;
@@ -458,7 +466,7 @@ static void emit_rewrite_lines(struct emit_callback *ecb,
        if (!endp) {
                const char *plain = diff_get_color(ecb->color_diff,
                                                   DIFF_PLAIN);
-               emit_line_0(ecb->file, plain, reset, '\\',
+               emit_line_0(ecb->opt, plain, reset, '\\',
                            nneof, strlen(nneof));
        }
 }
@@ -482,6 +490,13 @@ static void emit_rewrite_diff(const char *name_a,
        char *data_one, *data_two;
        size_t size_one, size_two;
        struct emit_callback ecbdata;
+       char *line_prefix = "";
+       struct strbuf *msgbuf;
+
+       if (o && o->output_prefix) {
+               msgbuf = o->output_prefix(o, o->output_prefix_data);
+               line_prefix = msgbuf->buf;
+       }
 
        if (diff_mnemonic_prefix && DIFF_OPT_TST(o, REVERSE_DIFF)) {
                a_prefix = o->b_prefix;
@@ -508,7 +523,7 @@ static void emit_rewrite_diff(const char *name_a,
        ecbdata.color_diff = color_diff;
        ecbdata.found_changesp = &o->found_changes;
        ecbdata.ws_rule = whitespace_rule(name_b ? name_b : name_a);
-       ecbdata.file = o->file;
+       ecbdata.opt = o;
        if (ecbdata.ws_rule & WS_BLANK_AT_EOF) {
                mmfile_t mf1, mf2;
                mf1.ptr = (char *)data_one;
@@ -523,9 +538,10 @@ static void emit_rewrite_diff(const char *name_a,
        lc_a = count_lines(data_one, size_one);
        lc_b = count_lines(data_two, size_two);
        fprintf(o->file,
-               "%s--- %s%s%s\n%s+++ %s%s%s\n%s@@ -",
-               metainfo, a_name.buf, name_a_tab, reset,
-               metainfo, b_name.buf, name_b_tab, reset, fraginfo);
+               "%s%s--- %s%s%s\n%s%s+++ %s%s%s\n%s%s@@ -",
+               line_prefix, metainfo, a_name.buf, name_a_tab, reset,
+               line_prefix, metainfo, b_name.buf, name_b_tab, reset,
+               line_prefix, fraginfo);
        print_line_count(o->file, lc_a);
        fprintf(o->file, " +");
        print_line_count(o->file, lc_b);
@@ -838,9 +854,17 @@ static void fn_out_consume(void *priv, char *line, unsigned long len)
        const char *meta = diff_get_color(ecbdata->color_diff, DIFF_METAINFO);
        const char *plain = diff_get_color(ecbdata->color_diff, DIFF_PLAIN);
        const char *reset = diff_get_color(ecbdata->color_diff, DIFF_RESET);
+       struct diff_options *o = ecbdata->opt;
+       char *line_prefix = "";
+       struct strbuf *msgbuf;
+
+       if (o && o->output_prefix) {
+               msgbuf = o->output_prefix(o, o->output_prefix_data);
+               line_prefix = msgbuf->buf;
+       }
 
        if (ecbdata->header) {
-               fprintf(ecbdata->file, "%s", ecbdata->header->buf);
+               fprintf(ecbdata->opt->file, "%s", ecbdata->header->buf);
                strbuf_reset(ecbdata->header);
                ecbdata->header = NULL;
        }
@@ -852,10 +876,10 @@ static void fn_out_consume(void *priv, char *line, unsigned long len)
                name_a_tab = strchr(ecbdata->label_path[0], ' ') ? "\t" : "";
                name_b_tab = strchr(ecbdata->label_path[1], ' ') ? "\t" : "";
 
-               fprintf(ecbdata->file, "%s--- %s%s%s\n",
-                       meta, ecbdata->label_path[0], reset, name_a_tab);
-               fprintf(ecbdata->file, "%s+++ %s%s%s\n",
-                       meta, ecbdata->label_path[1], reset, name_b_tab);
+               fprintf(ecbdata->opt->file, "%s%s--- %s%s%s\n",
+                       line_prefix, meta, ecbdata->label_path[0], reset, name_a_tab);
+               fprintf(ecbdata->opt->file, "%s%s+++ %s%s%s\n",
+                       line_prefix, meta, ecbdata->label_path[1], reset, name_b_tab);
                ecbdata->label_path[0] = ecbdata->label_path[1] = NULL;
        }
 
@@ -872,15 +896,15 @@ static void fn_out_consume(void *priv, char *line, unsigned long len)
                find_lno(line, ecbdata);
                emit_hunk_header(ecbdata, line, len);
                if (line[len-1] != '\n')
-                       putc('\n', ecbdata->file);
+                       putc('\n', ecbdata->opt->file);
                return;
        }
 
        if (len < 1) {
-               emit_line(ecbdata->file, reset, reset, line, len);
+               emit_line(ecbdata->opt, reset, reset, line, len);
                if (ecbdata->diff_words
                    && ecbdata->diff_words->type == DIFF_WORDS_PORCELAIN)
-                       fputs("~\n", ecbdata->file);
+                       fputs("~\n", ecbdata->opt->file);
                return;
        }
 
@@ -896,11 +920,11 @@ static void fn_out_consume(void *priv, char *line, unsigned long len)
                }
                diff_words_flush(ecbdata);
                if (ecbdata->diff_words->type == DIFF_WORDS_PORCELAIN) {
-                       emit_line(ecbdata->file, plain, reset, line, len);
-                       fputs("~\n", ecbdata->file);
+                       emit_line(ecbdata->opt, plain, reset, line, len);
+                       fputs("~\n", ecbdata->opt->file);
                } else {
                        /* don't print the prefix character */
-                       emit_line(ecbdata->file, plain, reset, line+1, len-1);
+                       emit_line(ecbdata->opt, plain, reset, line+1, len-1);
                }
                return;
        }
@@ -912,7 +936,7 @@ static void fn_out_consume(void *priv, char *line, unsigned long len)
                ecbdata->lno_in_preimage++;
                if (line[0] == ' ')
                        ecbdata->lno_in_postimage++;
-               emit_line(ecbdata->file, color, reset, line, len);
+               emit_line(ecbdata->opt, color, reset, line, len);
        } else {
                ecbdata->lno_in_postimage++;
                emit_add_line(reset, ecbdata, line + 1, len - 1);
@@ -1092,10 +1116,17 @@ static void show_stats(struct diffstat_t *data, struct diff_options *options)
        int total_files = data->nr;
        int width, name_width;
        const char *reset, *set, *add_c, *del_c;
+       const char *line_prefix = "";
+       struct strbuf *msg = NULL;
 
        if (data->nr == 0)
                return;
 
+       if (options->output_prefix) {
+               msg = options->output_prefix(options, options->output_prefix_data);
+               line_prefix = msg->buf;
+       }
+
        width = options->stat_width ? options->stat_width : 80;
        name_width = options->stat_name_width ? options->stat_name_width : 50;
 
@@ -1165,6 +1196,7 @@ static void show_stats(struct diffstat_t *data, struct diff_options *options)
                }
 
                if (data->files[i]->is_binary) {
+                       fprintf(options->file, "%s", line_prefix);
                        show_name(options->file, prefix, name, len);
                        fprintf(options->file, "  Bin ");
                        fprintf(options->file, "%s%"PRIuMAX"%s",
@@ -1177,6 +1209,7 @@ static void show_stats(struct diffstat_t *data, struct diff_options *options)
                        continue;
                }
                else if (data->files[i]->is_unmerged) {
+                       fprintf(options->file, "%s", line_prefix);
                        show_name(options->file, prefix, name, len);
                        fprintf(options->file, "  Unmerged\n");
                        continue;
@@ -1199,6 +1232,7 @@ static void show_stats(struct diffstat_t *data, struct diff_options *options)
                        add = scale_linear(add, width, max_change);
                        del = scale_linear(del, width, max_change);
                }
+               fprintf(options->file, "%s", line_prefix);
                show_name(options->file, prefix, name, len);
                fprintf(options->file, "%5"PRIuMAX"%s", added + deleted,
                                added + deleted ? " " : "");
@@ -1206,6 +1240,7 @@ static void show_stats(struct diffstat_t *data, struct diff_options *options)
                show_graph(options->file, '-', del, del_c, reset);
                fprintf(options->file, "\n");
        }
+       fprintf(options->file, "%s", line_prefix);
        fprintf(options->file,
               " %d files changed, %d insertions(+), %d deletions(-)\n",
               total_files, adds, dels);
@@ -1232,6 +1267,12 @@ static void show_shortstats(struct diffstat_t *data, struct diff_options *option
                        }
                }
        }
+       if (options->output_prefix) {
+               struct strbuf *msg = NULL;
+               msg = options->output_prefix(options,
+                               options->output_prefix_data);
+               fprintf(options->file, "%s", msg->buf);
+       }
        fprintf(options->file, " %d files changed, %d insertions(+), %d deletions(-)\n",
               total_files, adds, dels);
 }
@@ -1246,6 +1287,13 @@ static void show_numstat(struct diffstat_t *data, struct diff_options *options)
        for (i = 0; i < data->nr; i++) {
                struct diffstat_file *file = data->files[i];
 
+               if (options->output_prefix) {
+                       struct strbuf *msg = NULL;
+                       msg = options->output_prefix(options,
+                                       options->output_prefix_data);
+                       fprintf(options->file, "%s", msg->buf);
+               }
+
                if (file->is_binary)
                        fprintf(options->file, "-\t-\t");
                else
@@ -1281,10 +1329,18 @@ struct dirstat_dir {
        int alloc, nr, percent, cumulative;
 };
 
-static long gather_dirstat(FILE *file, struct dirstat_dir *dir, unsigned long changed, const char *base, int baselen)
+static long gather_dirstat(struct diff_options *opt, struct dirstat_dir *dir,
+               unsigned long changed, const char *base, int baselen)
 {
        unsigned long this_dir = 0;
        unsigned int sources = 0;
+       const char *line_prefix = "";
+       struct strbuf *msg = NULL;
+
+       if (opt->output_prefix) {
+               msg = opt->output_prefix(opt, opt->output_prefix_data);
+               line_prefix = msg->buf;
+       }
 
        while (dir->nr) {
                struct dirstat_file *f = dir->files;
@@ -1299,7 +1355,7 @@ static long gather_dirstat(FILE *file, struct dirstat_dir *dir, unsigned long ch
                slash = strchr(f->name + baselen, '/');
                if (slash) {
                        int newbaselen = slash + 1 - f->name;
-                       this = gather_dirstat(file, dir, changed, f->name, newbaselen);
+                       this = gather_dirstat(opt, dir, changed, f->name, newbaselen);
                        sources++;
                } else {
                        this = f->changed;
@@ -1321,7 +1377,8 @@ static long gather_dirstat(FILE *file, struct dirstat_dir *dir, unsigned long ch
                if (permille) {
                        int percent = permille / 10;
                        if (percent >= dir->percent) {
-                               fprintf(file, "%4d.%01d%% %.*s\n", percent, permille % 10, baselen, base);
+                               fprintf(opt->file, "%s%4d.%01d%% %.*s\n", line_prefix,
+                                       percent, permille % 10, baselen, base);
                                if (!dir->cumulative)
                                        return 0;
                        }
@@ -1401,7 +1458,7 @@ static void show_dirstat(struct diff_options *options)
 
        /* Show all directories with more than x% of the changes */
        qsort(dir.files, dir.nr, sizeof(dir.files[0]), dirstat_compare);
-       gather_dirstat(options->file, &dir, changed, "", 0);
+       gather_dirstat(options, &dir, changed, "", 0);
 }
 
 static void free_diffstat_info(struct diffstat_t *diffstat)
@@ -1459,6 +1516,15 @@ static void checkdiff_consume(void *priv, char *line, unsigned long len)
        const char *reset = diff_get_color(color_diff, DIFF_RESET);
        const char *set = diff_get_color(color_diff, DIFF_FILE_NEW);
        char *err;
+       char *line_prefix = "";
+       struct strbuf *msgbuf;
+
+       assert(data->o);
+       if (data->o->output_prefix) {
+               msgbuf = data->o->output_prefix(data->o,
+                       data->o->output_prefix_data);
+               line_prefix = msgbuf->buf;
+       }
 
        if (line[0] == '+') {
                unsigned bad;
@@ -1466,18 +1532,18 @@ static void checkdiff_consume(void *priv, char *line, unsigned long len)
                if (is_conflict_marker(line + 1, marker_size, len - 1)) {
                        data->status |= 1;
                        fprintf(data->o->file,
-                               "%s:%d: leftover conflict marker\n",
-                               data->filename, data->lineno);
+                               "%s%s:%d: leftover conflict marker\n",
+                               line_prefix, data->filename, data->lineno);
                }
                bad = ws_check(line + 1, len - 1, data->ws_rule);
                if (!bad)
                        return;
                data->status |= bad;
                err = whitespace_error_string(bad);
-               fprintf(data->o->file, "%s:%d: %s.\n",
-                       data->filename, data->lineno, err);
+               fprintf(data->o->file, "%s%s:%d: %s.\n",
+                       line_prefix, data->filename, data->lineno, err);
                free(err);
-               emit_line(data->o->file, set, reset, line, 1);
+               emit_line(data->o, set, reset, line, 1);
                ws_check_emit(line + 1, len - 1, data->ws_rule,
                              data->o->file, set, reset, ws);
        } else if (line[0] == ' ') {
@@ -1515,7 +1581,7 @@ static unsigned char *deflate_it(char *data,
        return deflated;
 }
 
-static void emit_binary_diff_body(FILE *file, mmfile_t *one, mmfile_t *two)
+static void emit_binary_diff_body(FILE *file, mmfile_t *one, mmfile_t *two, char *prefix)
 {
        void *cp;
        void *delta;
@@ -1544,13 +1610,13 @@ static void emit_binary_diff_body(FILE *file, mmfile_t *one, mmfile_t *two)
        }
 
        if (delta && delta_size < deflate_size) {
-               fprintf(file, "delta %lu\n", orig_size);
+               fprintf(file, "%sdelta %lu\n", prefix, orig_size);
                free(deflated);
                data = delta;
                data_size = delta_size;
        }
        else {
-               fprintf(file, "literal %lu\n", two->size);
+               fprintf(file, "%sliteral %lu\n", prefix, two->size);
                free(delta);
                data = deflated;
                data_size = deflate_size;
@@ -1568,18 +1634,19 @@ static void emit_binary_diff_body(FILE *file, mmfile_t *one, mmfile_t *two)
                        line[0] = bytes - 26 + 'a' - 1;
                encode_85(line + 1, cp, bytes);
                cp = (char *) cp + bytes;
+               fprintf(file, "%s", prefix);
                fputs(line, file);
                fputc('\n', file);
        }
-       fprintf(file, "\n");
+       fprintf(file, "%s\n", prefix);
        free(data);
 }
 
-static void emit_binary_diff(FILE *file, mmfile_t *one, mmfile_t *two)
+static void emit_binary_diff(FILE *file, mmfile_t *one, mmfile_t *two, char *prefix)
 {
-       fprintf(file, "GIT binary patch\n");
-       emit_binary_diff_body(file, one, two);
-       emit_binary_diff_body(file, two, one);
+       fprintf(file, "%sGIT binary patch\n", prefix);
+       emit_binary_diff_body(file, one, two, prefix);
+       emit_binary_diff_body(file, two, one, prefix);
 }
 
 static void diff_filespec_load_driver(struct diff_filespec *one)
@@ -1668,6 +1735,13 @@ static void builtin_diff(const char *name_a,
        struct userdiff_driver *textconv_one = NULL;
        struct userdiff_driver *textconv_two = NULL;
        struct strbuf header = STRBUF_INIT;
+       struct strbuf *msgbuf;
+       char *line_prefix = "";
+
+       if (o->output_prefix) {
+               msgbuf = o->output_prefix(o, o->output_prefix_data);
+               line_prefix = msgbuf->buf;
+       }
 
        if (DIFF_OPT_TST(o, SUBMODULE_LOG) &&
                        (!one->mode || S_ISGITLINK(one->mode)) &&
@@ -1702,22 +1776,22 @@ static void builtin_diff(const char *name_a,
        b_two = quote_two(b_prefix, name_b + (*name_b == '/'));
        lbl[0] = DIFF_FILE_VALID(one) ? a_one : "/dev/null";
        lbl[1] = DIFF_FILE_VALID(two) ? b_two : "/dev/null";
-       strbuf_addf(&header, "%sdiff --git %s %s%s\n", set, a_one, b_two, reset);
+       strbuf_addf(&header, "%s%sdiff --git %s %s%s\n", line_prefix, set, a_one, b_two, reset);
        if (lbl[0][0] == '/') {
                /* /dev/null */
-               strbuf_addf(&header, "%snew file mode %06o%s\n", set, two->mode, reset);
+               strbuf_addf(&header, "%s%snew file mode %06o%s\n", line_prefix, set, two->mode, reset);
                if (xfrm_msg && xfrm_msg[0])
                        strbuf_addf(&header, "%s%s%s\n", set, xfrm_msg, reset);
        }
        else if (lbl[1][0] == '/') {
-               strbuf_addf(&header, "%sdeleted file mode %06o%s\n", set, one->mode, reset);
+               strbuf_addf(&header, "%s%sdeleted file mode %06o%s\n", line_prefix, set, one->mode, reset);
                if (xfrm_msg && xfrm_msg[0])
                        strbuf_addf(&header, "%s%s%s\n", set, xfrm_msg, reset);
        }
        else {
                if (one->mode != two->mode) {
-                       strbuf_addf(&header, "%sold mode %06o%s\n", set, one->mode, reset);
-                       strbuf_addf(&header, "%snew mode %06o%s\n", set, two->mode, reset);
+                       strbuf_addf(&header, "%s%sold mode %06o%s\n", line_prefix, set, one->mode, reset);
+                       strbuf_addf(&header, "%s%snew mode %06o%s\n", line_prefix, set, two->mode, reset);
                }
                if (xfrm_msg && xfrm_msg[0])
                        strbuf_addf(&header, "%s%s%s\n", set, xfrm_msg, reset);
@@ -1752,10 +1826,10 @@ static void builtin_diff(const char *name_a,
                fprintf(o->file, "%s", header.buf);
                strbuf_reset(&header);
                if (DIFF_OPT_TST(o, BINARY))
-                       emit_binary_diff(o->file, &mf1, &mf2);
+                       emit_binary_diff(o->file, &mf1, &mf2, line_prefix);
                else
-                       fprintf(o->file, "Binary files %s and %s differ\n",
-                               lbl[0], lbl[1]);
+                       fprintf(o->file, "%sBinary files %s and %s differ\n",
+                               line_prefix, lbl[0], lbl[1]);
                o->found_changes = 1;
        }
        else {
@@ -1787,7 +1861,7 @@ static void builtin_diff(const char *name_a,
                ecbdata.ws_rule = whitespace_rule(name_b ? name_b : name_a);
                if (ecbdata.ws_rule & WS_BLANK_AT_EOF)
                        check_blank_at_eof(&mf1, &mf2, &ecbdata);
-               ecbdata.file = o->file;
+               ecbdata.opt = o;
                ecbdata.header = header.len ? &header : NULL;
                xpp.flags = XDF_NEED_MINIMAL | o->xdl_opts;
                xecfg.ctxlen = o->context;
@@ -2381,28 +2455,36 @@ static void fill_metainfo(struct strbuf *msg,
                          struct diff_options *o,
                          struct diff_filepair *p)
 {
+       struct strbuf *msgbuf;
+       char *line_prefix = "";
+
+       if (o->output_prefix) {
+               msgbuf = o->output_prefix(o, o->output_prefix_data);
+               line_prefix = msgbuf->buf;
+       }
+
        strbuf_init(msg, PATH_MAX * 2 + 300);
        switch (p->status) {
        case DIFF_STATUS_COPIED:
-               strbuf_addf(msg, "similarity index %d%%", similarity_index(p));
-               strbuf_addstr(msg, "\ncopy from ");
+               strbuf_addf(msg, "%ssimilarity index %d%%", line_prefix, similarity_index(p));
+               strbuf_addf(msg, "\n%scopy from ", line_prefix);
                quote_c_style(name, msg, NULL, 0);
-               strbuf_addstr(msg, "\ncopy to ");
+               strbuf_addf(msg, "\n%scopy to ", line_prefix);
                quote_c_style(other, msg, NULL, 0);
                strbuf_addch(msg, '\n');
                break;
        case DIFF_STATUS_RENAMED:
-               strbuf_addf(msg, "similarity index %d%%", similarity_index(p));
-               strbuf_addstr(msg, "\nrename from ");
+               strbuf_addf(msg, "%ssimilarity index %d%%", line_prefix, similarity_index(p));
+               strbuf_addf(msg, "\n%srename from ", line_prefix);
                quote_c_style(name, msg, NULL, 0);
-               strbuf_addstr(msg, "\nrename to ");
+               strbuf_addf(msg, "\n%srename to ", line_prefix);
                quote_c_style(other, msg, NULL, 0);
                strbuf_addch(msg, '\n');
                break;
        case DIFF_STATUS_MODIFIED:
                if (p->score) {
-                       strbuf_addf(msg, "dissimilarity index %d%%\n",
-                                   similarity_index(p));
+                       strbuf_addf(msg, "%sdissimilarity index %d%%\n",
+                                   line_prefix, similarity_index(p));
                        break;
                }
                /* fallthru */
@@ -2419,8 +2501,8 @@ static void fill_metainfo(struct strbuf *msg,
                            (!fill_mmfile(&mf, two) && diff_filespec_is_binary(two)))
                                abbrev = 40;
                }
-               strbuf_addf(msg, "index %.*s..%.*s",
-                           abbrev, sha1_to_hex(one->sha1),
+               strbuf_addf(msg, "%sindex %.*s..%.*s",
+                           line_prefix, abbrev, sha1_to_hex(one->sha1),
                            abbrev, sha1_to_hex(two->sha1));
                if (one->mode == two->mode)
                        strbuf_addf(msg, " %06o", one->mode);
@@ -3124,6 +3206,11 @@ static void diff_flush_raw(struct diff_filepair *p, struct diff_options *opt)
 {
        int line_termination = opt->line_termination;
        int inter_name_termination = line_termination ? '\t' : '\0';
+       if (opt->output_prefix) {
+               struct strbuf *msg = NULL;
+               msg = opt->output_prefix(opt, opt->output_prefix_data);
+               fprintf(opt->file, "%s", msg->buf);
+       }
 
        if (!(opt->output_format & DIFF_FORMAT_NAME_STATUS)) {
                fprintf(opt->file, ":%06o %06o %s ", p->one->mode, p->two->mode,
@@ -3369,48 +3456,62 @@ static void show_file_mode_name(FILE *file, const char *newdelete, struct diff_f
 }
 
 
-static void show_mode_change(FILE *file, struct diff_filepair *p, int show_name)
+static void show_mode_change(FILE *file, struct diff_filepair *p, int show_name,
+               const char *line_prefix)
 {
        if (p->one->mode && p->two->mode && p->one->mode != p->two->mode) {
-               fprintf(file, " mode change %06o => %06o%c", p->one->mode, p->two->mode,
-                       show_name ? ' ' : '\n');
+               fprintf(file, "%s mode change %06o => %06o%c", line_prefix, p->one->mode,
+                       p->two->mode, show_name ? ' ' : '\n');
                if (show_name) {
                        write_name_quoted(p->two->path, file, '\n');
                }
        }
 }
 
-static void show_rename_copy(FILE *file, const char *renamecopy, struct diff_filepair *p)
+static void show_rename_copy(FILE *file, const char *renamecopy, struct diff_filepair *p,
+                       const char *line_prefix)
 {
        char *names = pprint_rename(p->one->path, p->two->path);
 
        fprintf(file, " %s %s (%d%%)\n", renamecopy, names, similarity_index(p));
        free(names);
-       show_mode_change(file, p, 0);
+       show_mode_change(file, p, 0, line_prefix);
 }
 
-static void diff_summary(FILE *file, struct diff_filepair *p)
+static void diff_summary(struct diff_options *opt, struct diff_filepair *p)
 {
+       FILE *file = opt->file;
+       char *line_prefix = "";
+
+       if (opt->output_prefix) {
+               struct strbuf *buf = opt->output_prefix(opt, opt->output_prefix_data);
+               line_prefix = buf->buf;
+       }
+
        switch(p->status) {
        case DIFF_STATUS_DELETED:
+               fputs(line_prefix, file);
                show_file_mode_name(file, "delete", p->one);
                break;
        case DIFF_STATUS_ADDED:
+               fputs(line_prefix, file);
                show_file_mode_name(file, "create", p->two);
                break;
        case DIFF_STATUS_COPIED:
-               show_rename_copy(file, "copy", p);
+               fputs(line_prefix, file);
+               show_rename_copy(file, "copy", p, line_prefix);
                break;
        case DIFF_STATUS_RENAMED:
-               show_rename_copy(file, "rename", p);
+               fputs(line_prefix, file);
+               show_rename_copy(file, "rename", p, line_prefix);
                break;
        default:
                if (p->score) {
-                       fputs(" rewrite ", file);
+                       fprintf(file, "%s rewrite ", line_prefix);
                        write_name_quoted(p->two->path, file, ' ');
                        fprintf(file, "(%d%%)\n", similarity_index(p));
                }
-               show_mode_change(file, p, !p->score);
+               show_mode_change(file, p, !p->score, line_prefix);
                break;
        }
 }
@@ -3619,8 +3720,9 @@ void diff_flush(struct diff_options *options)
                show_dirstat(options);
 
        if (output_format & DIFF_FORMAT_SUMMARY && !is_summary_empty(q)) {
-               for (i = 0; i < q->nr; i++)
-                       diff_summary(options->file, q->queue[i]);
+               for (i = 0; i < q->nr; i++) {
+                       diff_summary(options, q->queue[i]);
+               }
                separator++;
        }