10 files changed, 194 insertions, 18 deletions

diff --git a/cgit.c b/cgit.c
index baad1c8..d84b4be 100644
--- a/cgit.c
+++ b/cgit.c
@@ -152,6 +152,8 @@ static void config_cb(const char *name, const char *value)
                 ctx.cfg.snapshots = cgit_parse_snapshots_mask(value);
         else if (!strcmp(name, "enable-filter-overrides"))
                 ctx.cfg.enable_filter_overrides = atoi(value);
+        else if (!strcmp(name, "enable-follow-links"))
+                ctx.cfg.enable_follow_links = atoi(value);
         else if (!strcmp(name, "enable-http-clone"))
                 ctx.cfg.enable_http_clone = atoi(value);
         else if (!strcmp(name, "enable-index-links"))
@@ -333,6 +335,8 @@ static void querystring_cb(const char *name, const char *value)
                 ctx.qry.context = atoi(value);
         } else if (!strcmp(name, "ignorews")) {
                 ctx.qry.ignorews = atoi(value);
+        } else if (!strcmp(name, "follow")) {
+                ctx.qry.follow = atoi(value);
         }
 }
 
diff --git a/cgit.h b/cgit.h
index b2253d2..3120562 100644
--- a/cgit.h
+++ b/cgit.h
@@ -179,6 +179,7 @@ struct cgit_query {
         int show_all;
         int context;
         int ignorews;
+        int follow;
         char *vpath;
 };
 
@@ -221,6 +222,7 @@ struct cgit_config {
         int case_sensitive_sort;
         int embedded;
         int enable_filter_overrides;
+        int enable_follow_links;
         int enable_http_clone;
         int enable_index_links;
         int enable_index_owner;
diff --git a/cgitrc.5.txt b/cgitrc.5.txt
index e21ece9..759f353 100644
--- a/cgitrc.5.txt
+++ b/cgitrc.5.txt
@@ -150,6 +150,10 @@ enable-filter-overrides::
         Flag which, when set to "1", allows all filter settings to be
         overridden in repository-specific cgitrc files. Default value: none.
 
+enable-follow-links::
+        Flag which, when set to "1", allows users to follow a file in the log
+        view.  Default value: "0".
+
 enable-http-clone::
         If set to "1", cgit will act as an dumb HTTP endpoint for git clones.
         You can add "http://$HTTP_HOST$SCRIPT_NAME/$CGIT_REPO_URL" to clone-url
diff --git a/ui-diff.c b/ui-diff.c
index 1cf2ce0..caebd5d 100644
--- a/ui-diff.c
+++ b/ui-diff.c
@@ -36,6 +36,7 @@ static struct fileinfo {
 
 static int use_ssdiff = 0;
 static struct diff_filepair *current_filepair;
+static const char *current_prefix;
 
 struct diff_filespec *cgit_get_current_old_file(void)
 {
@@ -132,11 +133,30 @@ static void count_diff_lines(char *line, int len)
         }
 }
 
+static int show_filepair(struct diff_filepair *pair)
+{
+        /* Always show if we have no limiting prefix. */
+        if (!current_prefix)
+                return 1;
+
+        /* Show if either path in the pair begins with the prefix. */
+        if (starts_with(pair->one->path, current_prefix) ||
+            starts_with(pair->two->path, current_prefix))
+                return 1;
+
+        /* Otherwise we don't want to show this filepair. */
+        return 0;
+}
+
 static void inspect_filepair(struct diff_filepair *pair)
 {
         int binary = 0;
         unsigned long old_size = 0;
         unsigned long new_size = 0;
+
+        if (!show_filepair(pair))
+                return;
+
         files++;
         lines_added = 0;
         lines_removed = 0;
@@ -279,6 +299,9 @@ static void filepair_cb(struct diff_filepair *pair)
         int binary = 0;
         linediff_fn print_line_fn = print_line;
 
+        if (!show_filepair(pair))
+                return;
+
         current_filepair = pair;
         if (use_ssdiff) {
                 cgit_ssdiff_header_begin();
@@ -365,6 +388,18 @@ void cgit_print_diff(const char *new_rev, const char *old_rev,
         const unsigned char *old_tree_sha1, *new_tree_sha1;
         diff_type difftype;
 
+        /*
+         * If "follow" is set then the diff machinery needs to examine the
+         * entire commit to detect renames so we must limit the paths in our
+         * own callbacks and not pass the prefix to the diff machinery.
+         */
+        if (ctx.qry.follow && ctx.cfg.enable_follow_links) {
+                current_prefix = prefix;
+                prefix = "";
+        } else {
+                current_prefix = NULL;
+        }
+
         if (!new_rev)
                 new_rev = ctx.qry.head;
         if (get_sha1(new_rev, new_rev_sha1)) {
diff --git a/ui-log.c b/ui-log.c
index 8028b27..ff832ce 100644
--- a/ui-log.c
+++ b/ui-log.c
@@ -12,7 +12,7 @@
 #include "ui-shared.h"
 #include "argv-array.h"
 
-static int files, add_lines, rem_lines;
+static int files, add_lines, rem_lines, lines_counted;
 
 /*
  * The list of available column colors in the commit graph.
@@ -67,7 +67,7 @@ void show_commit_decorations(struct commit *commit)
                         strncpy(buf, deco->name + 11, sizeof(buf) - 1);
                         cgit_log_link(buf, NULL, "branch-deco", buf, NULL,
                                       ctx.qry.vpath, 0, NULL, NULL,
-                                      ctx.qry.showmsg);
+                                      ctx.qry.showmsg, 0);
                 }
                 else if (starts_with(deco->name, "tag: refs/tags/")) {
                         strncpy(buf, deco->name + 15, sizeof(buf) - 1);
@@ -84,7 +84,7 @@ void show_commit_decorations(struct commit *commit)
                         cgit_log_link(buf, NULL, "remote-deco", NULL,
                                       sha1_to_hex(commit->object.sha1),
                                       ctx.qry.vpath, 0, NULL, NULL,
-                                      ctx.qry.showmsg);
+                                      ctx.qry.showmsg, 0);
                 }
                 else {
                         strncpy(buf, deco->name, sizeof(buf) - 1);
@@ -98,6 +98,74 @@ next:
         html("</span>");
 }
 
+static void handle_rename(struct diff_filepair *pair)
+{
+        /*
+         * After we have seen a rename, we generate links to the previous
+         * name of the file so that commit & diff views get fed the path
+         * that is correct for the commit they are showing, avoiding the
+         * need to walk the entire history leading back to every commit we
+         * show in order detect renames.
+         */
+        if (0 != strcmp(ctx.qry.vpath, pair->two->path)) {
+                free(ctx.qry.vpath);
+                ctx.qry.vpath = xstrdup(pair->two->path);
+        }
+        inspect_files(pair);
+}
+
+static int show_commit(struct commit *commit, struct rev_info *revs)
+{
+        struct commit_list *parents = commit->parents;
+        struct commit *parent;
+        int found = 0, saved_fmt;
+        unsigned saved_flags = revs->diffopt.flags;
+
+
+        /* Always show if we're not in "follow" mode with a single file. */
+        if (!ctx.qry.follow)
+                return 1;
+
+        /*
+         * In "follow" mode, we don't show merges.  This is consistent with
+         * "git log --follow -- <file>".
+         */
+        if (parents && parents->next)
+                return 0;
+
+        /*
+         * If this is the root commit, do what rev_info tells us.
+         */
+        if (!parents)
+                return revs->show_root_diff;
+
+        /* When we get here we have precisely one parent. */
+        parent = parents->item;
+        parse_commit(parent);
+
+        files = 0;
+        add_lines = 0;
+        rem_lines = 0;
+
+        DIFF_OPT_SET(&revs->diffopt, RECURSIVE);
+        diff_tree_sha1(parent->tree->object.sha1,
+                       commit->tree->object.sha1,
+                       "", &revs->diffopt);
+        diffcore_std(&revs->diffopt);
+
+        found = !diff_queue_is_empty();
+        saved_fmt = revs->diffopt.output_format;
+        revs->diffopt.output_format = DIFF_FORMAT_CALLBACK;
+        revs->diffopt.format_callback = cgit_diff_tree_cb;
+        revs->diffopt.format_callback_data = handle_rename;
+        diff_flush(&revs->diffopt);
+        revs->diffopt.output_format = saved_fmt;
+        revs->diffopt.flags = saved_flags;
+
+        lines_counted = 1;
+        return found;
+}
+
 static void print_commit(struct commit *commit, struct rev_info *revs)
 {
         struct commitinfo *info;
@@ -177,7 +245,8 @@ static void print_commit(struct commit *commit, struct rev_info *revs)
                 cgit_print_age(commit->date, TM_WEEK * 2, FMT_SHORTDATE);
         }
 
-        if (ctx.repo->enable_log_filecount || ctx.repo->enable_log_linecount) {
+        if (!lines_counted && (ctx.repo->enable_log_filecount ||
+                               ctx.repo->enable_log_linecount)) {
                 files = 0;
                 add_lines = 0;
                 rem_lines = 0;
@@ -325,7 +394,17 @@ void cgit_print_log(const char *tip, int ofs, int cnt, char *grep, char *pattern
                         }
                 }
         }
-        if (commit_graph) {
+
+        if (!path || !ctx.cfg.enable_follow_links) {
+                /*
+                 * If we don't have a path, "follow" is a no-op so make sure
+                 * the variable is set to false to avoid needing to check
+                 * both this and whether we have a path everywhere.
+                 */
+                ctx.qry.follow = 0;
+        }
+
+        if (commit_graph && !ctx.qry.follow) {
                 argv_array_push(&rev_argv, "--graph");
                 argv_array_push(&rev_argv, "--color");
                 graph_set_column_colors(column_colors_html,
@@ -337,6 +416,8 @@ void cgit_print_log(const char *tip, int ofs, int cnt, char *grep, char *pattern
         else if (commit_sort == 2)
                 argv_array_push(&rev_argv, "--topo-order");
 
+        if (path && ctx.qry.follow)
+                argv_array_push(&rev_argv, "--follow");
         argv_array_push(&rev_argv, "--");
         if (path)
                 argv_array_push(&rev_argv, path);
@@ -347,10 +428,17 @@ void cgit_print_log(const char *tip, int ofs, int cnt, char *grep, char *pattern
         rev.verbose_header = 1;
         rev.show_root_diff = 0;
         rev.ignore_missing = 1;
+        rev.simplify_history = 1;
         setup_revisions(rev_argv.argc, rev_argv.argv, &rev, NULL);
         load_ref_decorations(DECORATE_FULL_REFS);
         rev.show_decorations = 1;
         rev.grep_filter.regflags |= REG_ICASE;
+
+        rev.diffopt.detect_rename = 1;
+        rev.diffopt.rename_limit = ctx.cfg.renamelimit;
+        if (ctx.qry.ignorews)
+                DIFF_XDL_SET(&rev.diffopt, IGNORE_WHITESPACE);
+
         compile_grep_patterns(&rev.grep_filter);
         prepare_revision_walk(&rev);
 
@@ -368,11 +456,12 @@ void cgit_print_log(const char *tip, int ofs, int cnt, char *grep, char *pattern
                 cgit_log_link(ctx.qry.showmsg ? "Collapse" : "Expand", NULL,
                               NULL, ctx.qry.head, ctx.qry.sha1,
                               ctx.qry.vpath, ctx.qry.ofs, ctx.qry.grep,
-                              ctx.qry.search, ctx.qry.showmsg ? 0 : 1);
+                              ctx.qry.search, ctx.qry.showmsg ? 0 : 1,
+                              ctx.qry.follow);
                 html(")");
         }
         html("</th><th class='left'>Author</th>");
-        if (commit_graph)
+        if (rev.graph)
                 html("<th class='left'>Age</th>");
         if (ctx.repo->enable_log_filecount) {
                 html("<th class='left'>Files</th>");
@@ -388,13 +477,30 @@ void cgit_print_log(const char *tip, int ofs, int cnt, char *grep, char *pattern
                 ofs = 0;
 
         for (i = 0; i < ofs && (commit = get_revision(&rev)) != NULL; i++) {
+                if (show_commit(commit, &rev))
+                        i++;
                 free_commit_buffer(commit);
                 free_commit_list(commit->parents);
                 commit->parents = NULL;
         }
 
         for (i = 0; i < cnt && (commit = get_revision(&rev)) != NULL; i++) {
-                print_commit(commit, &rev);
+                /*
+                 * In "follow" mode, we must count the files and lines the
+                 * first time we invoke diff on a given commit, and we need
+                 * to do that to see if the commit touches the path we care
+                 * about, so we do it in show_commit.  Hence we must clear
+                 * lines_counted here.
+                 *
+                 * This has the side effect of avoiding running diff twice
+                 * when we are both following renames and showing file
+                 * and/or line counts.
+                 */
+                lines_counted = 0;
+                if (show_commit(commit, &rev)) {
+                        i++;
+                        print_commit(commit, &rev);
+                }
                 free_commit_buffer(commit);
                 free_commit_list(commit->parents);
                 commit->parents = NULL;
@@ -406,7 +512,8 @@ void cgit_print_log(const char *tip, int ofs, int cnt, char *grep, char *pattern
                         cgit_log_link("[prev]", NULL, NULL, ctx.qry.head,
                                       ctx.qry.sha1, ctx.qry.vpath,
                                       ofs - cnt, ctx.qry.grep,
-                                      ctx.qry.search, ctx.qry.showmsg);
+                                      ctx.qry.search, ctx.qry.showmsg,
+                                      ctx.qry.follow);
                         html("</li>");
                 }
                 if ((commit = get_revision(&rev)) != NULL) {
@@ -414,14 +521,16 @@ void cgit_print_log(const char *tip, int ofs, int cnt, char *grep, char *pattern
                         cgit_log_link("[next]", NULL, NULL, ctx.qry.head,
                                       ctx.qry.sha1, ctx.qry.vpath,
                                       ofs + cnt, ctx.qry.grep,
-                                      ctx.qry.search, ctx.qry.showmsg);
+                                      ctx.qry.search, ctx.qry.showmsg,
+                                      ctx.qry.follow);
                         html("</li>");
                 }
                 html("</ul>");
         } else if ((commit = get_revision(&rev)) != NULL) {
                 htmlf("<tr class='nohover'><td colspan='%d'>", columns);
                 cgit_log_link("[...]", NULL, NULL, ctx.qry.head, NULL,
-                              ctx.qry.vpath, 0, NULL, NULL, ctx.qry.showmsg);
+                              ctx.qry.vpath, 0, NULL, NULL, ctx.qry.showmsg,
+                              ctx.qry.follow);
                 html("</td></tr>\n");
         }
 
diff --git a/ui-refs.c b/ui-refs.c
index d3d71dd..73a187b 100644
--- a/ui-refs.c
+++ b/ui-refs.c
@@ -63,7 +63,7 @@ static int print_branch(struct refinfo *ref)
                 return 1;
         html("<tr><td>");
         cgit_log_link(name, NULL, NULL, name, NULL, NULL, 0, NULL, NULL,
-                      ctx.qry.showmsg);
+                      ctx.qry.showmsg, 0);
         html("</td><td>");
 
         if (ref->object->type == OBJ_COMMIT) {
diff --git a/ui-repolist.c b/ui-repolist.c
index 2453a7f..edefc4c 100644
--- a/ui-repolist.c
+++ b/ui-repolist.c
@@ -330,7 +330,7 @@ void cgit_print_repolist(void)
                         html("<td>");
                         cgit_summary_link("summary", NULL, "button", NULL);
                         cgit_log_link("log", NULL, "button", NULL, NULL, NULL,
-                                      0, NULL, NULL, ctx.qry.showmsg);
+                                      0, NULL, NULL, ctx.qry.showmsg, 0);
                         cgit_tree_link("tree", NULL, "button", NULL, NULL, NULL);
                         html("</td>");
                 }
diff --git a/ui-shared.c b/ui-shared.c
index 4f84b7c..6be0c2e 100644
--- a/ui-shared.c
+++ b/ui-shared.c
@@ -303,7 +303,8 @@ void cgit_plain_link(const char *name, const char *title, const char *class,
 
 void cgit_log_link(const char *name, const char *title, const char *class,
                    const char *head, const char *rev, const char *path,
-                   int ofs, const char *grep, const char *pattern, int showmsg)
+                   int ofs, const char *grep, const char *pattern, int showmsg,
+                   int follow)
 {
         char *delim;
 
@@ -332,6 +333,11 @@ void cgit_log_link(const char *name, const char *title, const char *class,
         if (showmsg) {
                 html(delim);
                 html("showmsg=1");
+                delim = "&amp;";
+        }
+        if (follow) {
+                html(delim);
+                html("follow=1");
         }
         html("'>");
         html_txt(name);
@@ -373,6 +379,10 @@ void cgit_commit_link(char *name, const char *title, const char *class,
                 html("ignorews=1");
                 delim = "&amp;";
         }
+        if (ctx.qry.follow) {
+                html(delim);
+                html("follow=1");
+        }
         html("'>");
         if (name[0] != '\0')
                 html_txt(name);
@@ -429,6 +439,10 @@ void cgit_diff_link(const char *name, const char *title, const char *class,
                 html("ignorews=1");
                 delim = "&amp;";
         }
+        if (ctx.qry.follow) {
+                html(delim);
+                html("follow=1");
+        }
         html("'>");
         html_txt(name);
         html("</a>");
@@ -469,7 +483,7 @@ static void cgit_self_link(char *name, const char *title, const char *class)
                               ctx.qry.has_sha1 ? ctx.qry.sha1 : NULL,
                               ctx.qry.path, ctx.qry.ofs,
                               ctx.qry.grep, ctx.qry.search,
-                              ctx.qry.showmsg);
+                              ctx.qry.showmsg, ctx.qry.follow);
         else if (!strcmp(ctx.qry.page, "commit"))
                 cgit_commit_link(name, title, class, ctx.qry.head,
                                  ctx.qry.has_sha1 ? ctx.qry.sha1 : NULL,
@@ -945,7 +959,7 @@ void cgit_print_pageheader(void)
                                ctx.qry.sha1, NULL);
                 cgit_log_link("log", NULL, hc("log"), ctx.qry.head,
                               NULL, ctx.qry.vpath, 0, NULL, NULL,
-                              ctx.qry.showmsg);
+                              ctx.qry.showmsg, ctx.qry.follow);
                 cgit_tree_link("tree", NULL, hc("tree"), ctx.qry.head,
                                ctx.qry.sha1, ctx.qry.vpath);
                 cgit_commit_link("commit", NULL, hc("commit"),
@@ -993,6 +1007,14 @@ void cgit_print_pageheader(void)
                 html("<div class='path'>");
                 html("path: ");
                 cgit_print_path_crumbs(ctx.qry.vpath);
+                if (ctx.cfg.enable_follow_links && !strcmp(ctx.qry.page, "log")) {
+                        html(" (");
+                        ctx.qry.follow = !ctx.qry.follow;
+                        cgit_self_link(ctx.qry.follow ? "follow" : "unfollow",
+                                        NULL, NULL);
+                        ctx.qry.follow = !ctx.qry.follow;
+                        html(")");
+                }
                 html("</div>");
         }
         html("<div class='content'>");
diff --git a/ui-shared.h b/ui-shared.h
index 43d0fa6..788b1bc 100644
--- a/ui-shared.h
+++ b/ui-shared.h
@@ -31,7 +31,7 @@ extern void cgit_plain_link(const char *name, const char *title,
 extern void cgit_log_link(const char *name, const char *title,
                           const char *class, const char *head, const char *rev,
                           const char *path, int ofs, const char *grep,
-                          const char *pattern, int showmsg);
+                          const char *pattern, int showmsg, int follow);
 extern void cgit_commit_link(char *name, const char *title,
                              const char *class, const char *head,
                              const char *rev, const char *path);
diff --git a/ui-tree.c b/ui-tree.c
index bbc468e..c8d24f6 100644
--- a/ui-tree.c
+++ b/ui-tree.c
@@ -166,7 +166,7 @@ static int ls_item(const unsigned char *sha1, struct strbuf *base,
         html("<td>");
         cgit_log_link("log", NULL, "button", ctx.qry.head,
                       walk_tree_ctx->curr_rev, fullpath.buf, 0, NULL, NULL,
-                      ctx.qry.showmsg);
+                      ctx.qry.showmsg, 0);
         if (ctx.repo->max_stats)
                 cgit_stats_link("stats", NULL, "button", ctx.qry.head,
                                 fullpath.buf);