Diff: -l<num> to limit rename/copy detection.

When many paths are modified, rename detection takes a lot of time.
The new option -l<num> can be used to disable rename detection when
more than <num> paths are possibly created as renames.

Signed-off-by: Junio C Hamano <junkio@cox.net>

diff --git a/Documentation/diff-options.txt b/Documentation/diff-options.txt
index 48cf93c..616d4a4 100644 (file)
--- a/Documentation/diff-options.txt
+++ b/Documentation/diff-options.txt
@@ -35,6 +35,13 @@
        copy.  This is a very expensive operation for large
        projects, so use it with caution.
 
+-l<num>::
+       -M and -C options require O(n^2) processing time where n
+       in the number of potential rename/copy targets.  This
+       option prevents rename/copy detection from running if
+       the number of rename/copy targets exceed the specified
+       number.
+
 -S<string>::
        Look for differences that contains the change in <string>.
 

diff --git a/diff.c b/diff.c
index 77d3166..cafc755 100644 (file)
--- a/diff.c
+++ b/diff.c
@@ -674,11 +674,12 @@ void diff_setup(struct diff_options *options)
        options->output_format = DIFF_FORMAT_RAW;
        options->line_termination = '\n';
        options->break_opt = -1;
+       options->rename_limit = -1;
 }
 
 int diff_setup_done(struct diff_options *options)
 {
-       if (options->find_copies_harder &&
+       if ((options->find_copies_harder || 0 <= options->rename_limit) &&
            options->detect_rename != DIFF_DETECT_COPY)
                return -1;
        if (options->setup & DIFF_SETUP_USE_CACHE) {
@@ -704,6 +705,8 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
                options->output_format = DIFF_FORMAT_PATCH;
        else if (!strcmp(arg, "-z"))
                options->line_termination = 0;
+       else if (!strncmp(arg, "-l", 2))
+               options->rename_limit = strtoul(arg+2, NULL, 10);
        else if (!strcmp(arg, "--name-only"))
                options->output_format = DIFF_FORMAT_NAME;
        else if (!strcmp(arg, "-R"))
@@ -1141,7 +1144,7 @@ void diffcore_std(struct diff_options *options)
        if (options->break_opt != -1)
                diffcore_break(options->break_opt);
        if (options->detect_rename)
-               diffcore_rename(options->detect_rename, options->rename_score);
+               diffcore_rename(options);
        if (options->break_opt != -1)
                diffcore_merge_broken();
        if (options->pickaxe)

diff --git a/diff.h b/diff.h
index 5800f15..2e32870 100644 (file)
--- a/diff.h
+++ b/diff.h
@@ -21,6 +21,7 @@ struct diff_options {
        int pickaxe_opts;
        int rename_score;
        int reverse_diff;
+       int rename_limit;
        int setup;
 };
 
@@ -61,23 +62,22 @@ extern void diffcore_std_no_resolve(struct diff_options *);
 
 #define COMMON_DIFF_OPTIONS_HELP \
 "\ncommon diff options:\n" \
-"  -r          diff recursively (only meaningful in diff-tree)\n" \
-"  -z          output diff-raw with lines terminated with NUL.\n" \
-"  -p          output patch format.\n" \
-"  -u          synonym for -p.\n" \
-"  --name-only show only names of changed files.\n" \
-"  --name-only-z\n" \
-"              same as --name-only but terminate lines with NUL.\n" \
-"  -R          swap input file pairs.\n" \
-"  -B          detect complete rewrites.\n" \
-"  -M          detect renames.\n" \
-"  -C          detect copies.\n" \
+"  -r            diff recursively (only meaningful in diff-tree)\n" \
+"  -z            output diff-raw with lines terminated with NUL.\n" \
+"  -p            output patch format.\n" \
+"  -u            synonym for -p.\n" \
+"  --name-only   show only names of changed files.\n" \
+"  -R            swap input file pairs.\n" \
+"  -B            detect complete rewrites.\n" \
+"  -M            detect renames.\n" \
+"  -C            detect copies.\n" \
 "  --find-copies-harder\n" \
-"              try unchanged files as candidate for copy detection.\n" \
-"  -O<file>    reorder diffs according to the <file>.\n" \
-"  -S<string>  find filepair whose only one side contains the string.\n" \
+"                try unchanged files as candidate for copy detection.\n" \
+"  -l<n>         limit rename attempts up to <n> paths.\n" \
+"  -O<file>      reorder diffs according to the <file>.\n" \
+"  -S<string>    find filepair whose only one side contains the string.\n" \
 "  --pickaxe-all\n" \
-"              show all files diff when -S is used and hit is found.\n"
+"                show all files diff when -S is used and hit is found.\n"
 
 extern int diff_queue_is_empty(void);
 

diff --git a/diffcore-rename.c b/diffcore-rename.c
index 092cf68..e17dd90 100644 (file)
--- a/diffcore-rename.c
+++ b/diffcore-rename.c
@@ -249,8 +249,11 @@ static int compute_stays(struct diff_queue_struct *q,
        return 1;
 }
 
-void diffcore_rename(int detect_rename, int minimum_score)
+void diffcore_rename(struct diff_options *options)
 {
+       int detect_rename = options->detect_rename;
+       int minimum_score = options->rename_score;
+       int rename_limit = options->rename_limit;
        struct diff_queue_struct *q = &diff_queued_diff;
        struct diff_queue_struct outq;
        struct diff_score *mx;
@@ -279,7 +282,8 @@ void diffcore_rename(int detect_rename, int minimum_score)
                else if (detect_rename == DIFF_DETECT_COPY)
                        register_rename_src(p->one, 1);
        }
-       if (rename_dst_nr == 0)
+       if (rename_dst_nr == 0 ||
+           (0 <= rename_limit && rename_limit < rename_dst_nr))
                goto cleanup; /* nothing to do */
 
        /* We really want to cull the candidates list early

diff --git a/diffcore.h b/diffcore.h
index f1b5ca7..a38acb1 100644 (file)
--- a/diffcore.h
+++ b/diffcore.h
@@ -85,7 +85,7 @@ extern void diff_q(struct diff_queue_struct *, struct diff_filepair *);
 
 extern void diffcore_pathspec(const char **pathspec);
 extern void diffcore_break(int);
-extern void diffcore_rename(int rename_copy, int);
+extern void diffcore_rename(struct diff_options *);
 extern void diffcore_merge_broken(void);
 extern void diffcore_pickaxe(const char *needle, int opts);
 extern void diffcore_order(const char *orderfile);