cgit

commit 30304d8156a72ffc95e45e1aa9407319b81bd253

Author: John Keeping <john@keeping.me.uk>

log: allow users to follow a file

Teach the "log" UI to behave in the same way as "git log --follow", when
given a suitable instruction by the user.  The default behaviour remains
to show the log without following renames, but the follow behaviour can
be activated by following a link in the page header.

Follow is not the default because outputting merges in follow mode is
tricky ("git log --follow" will not show merges).  We also disable the
graph in follow mode because the commit graph is not simplified so we
end up with frequent gaps in the graph and many lines that do not
connect with any commits we're actually showing.

We also teach the "diff" and "commit" UIs to respect the follow flag on
URLs, causing the single-file version of these UIs to detect renames.
This feature is needed only for commits that rename the path we're
interested in.

For commits before the file has been renamed (i.e. that appear later in
the log list) we change the file path in the links from the log to point
to the old name; this means that links to commits always limit by the
path known to that commit.  If we didn't do this we would need to walk
down the log diff'ing every commit whenever we want to show a commit.
The drawback is that the "Log" link in the top bar of such a page links
to the log limited by the old name, so it will only show pre-rename
commits.  I consider this a reasonable trade-off since the "Back" button
still works and the log matches the path displayed in the top bar.

Since following renames requires running diff on every commit we
consider, I've added a knob to the configuration file to globally
enable/disable this feature.  Note that we may consider a large number
of commits the revision walking machinery no longer performs any path
limitation so we have to examine every commit until we find a page full
of commits that affect the target path or something related to it.

Suggested-by: René Neumann <necoro@necoro.eu>
Signed-off-by: John Keeping <john@keeping.me.uk>


 cgit.c | 4 +
 cgit.h | 2 
 cgitrc.5.txt | 4 +
 ui-diff.c | 35 ++++++++++++++
 ui-log.c | 131 ++++++++++++++++++++++++++++++++++++++++++++++++----
 ui-refs.c | 2 
 ui-repolist.c | 2 
 ui-shared.c | 28 ++++++++++-
 ui-shared.h | 2 
 ui-tree.c | 2 


diff --git a/cgit.c b/cgit.c
index baad1c8696fdbd38cf1cd12744cf8c298da9e6dc..d84b4be370bb17136430ffe40b2aa1e7eb677232 100644
--- a/cgit.c
+++ b/cgit.c
@@ -152,6 +152,8 @@ 	else if (!strcmp(name, "snapshots"))
 		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 @@ 	} else if (!strcmp(name, "context")) {
 		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 b2253d22b078a3377f1879880819b60658a7172b..31205622d49784bfca1beb8ba12d2f9c0431c6ed 100644
--- a/cgit.h
+++ b/cgit.h
@@ -179,6 +179,7 @@ 	diff_type difftype;
 	int show_all;
 	int context;
 	int ignorews;
+	int follow;
 	char *vpath;
 };
 
@@ -221,6 +222,7 @@ 	int cache_snapshot_ttl;
 	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 e21ece9fd30263b6f8244cf4d86c7a675d0024d8..759f353efaf7651d0372e64e8501a30c2398ee38 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 1cf2ce0c8e32b1a600b855c0d9951297d2fdcafa..caebd5d9eea61053cdcf8c85672acd506a9e0b52 100644
--- a/ui-diff.c
+++ b/ui-diff.c
@@ -36,6 +36,7 @@ } *items;
 
 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 @@ 			lines_removed++;
 	}
 }
 
+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 @@ 	unsigned long new_size = 0;
 	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();
@@ -364,6 +387,18 @@ {
 	struct commit *commit, *commit2;
 	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;




diff --git a/ui-log.c b/ui-log.c
index 8028b27a0679f006ffae5a724d307b8e3bc73e6e..ff832cee9adcaf9519cfcda5cff2748ae9ba6b3a 100644
--- a/ui-log.c
+++ b/ui-log.c
@@ -12,7 +12,7 @@ #include "html.h"
 #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 @@ 		if (starts_with(deco->name, "refs/heads/")) {
 			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 @@ 			strncpy(buf, deco->name + 13, sizeof(buf) - 1);
 			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 @@ 	}
 	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 @@ 		html("");
 		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 @@ 				argv_array_push(&rev_argv, arg);
 			}
 		}
 	}
-	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 @@ 		argv_array_push(&rev_argv, "--date-order");
 	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 @@ 	rev.commit_format = CMIT_FMT_DEFAULT;
 	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 @@ 		html(" (");
 		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 @@ 	if (ofs<0)
 		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 @@ 			html("
  • ");
 			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 @@ 			html("
  • ");
 			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 d3d71dd0d9a6aa18c7ead4cdabcce672b606f310..73a187be5b0c502facefced6720d26d3e1601eb2 100644
--- a/ui-refs.c
+++ b/ui-refs.c
@@ -63,7 +63,7 @@ 	if (!info)
 		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 2453a7f4a4229d5bbb7479a87b928593618acb35..edefc4c713145c6f67515738cfe468a2959ee478 100644
--- a/ui-repolist.c
+++ b/ui-repolist.c
@@ -330,7 +330,7 @@ 		if (ctx.cfg.enable_index_links) {
 			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 4f84b7c60e8570331353961497f1df7db340c106..6be0c2e3297b0cb406bfd6bfff40356dc9ed5e9f 100644
--- a/ui-shared.c
+++ b/ui-shared.c
@@ -303,7 +303,8 @@ }
 
 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 @@ 	}
 	if (showmsg) {
 		html(delim);
 		html("showmsg=1");
+		delim = "&amp;";
+	}
+	if (follow) {
+		html(delim);
+		html("follow=1");
 	}
 	html("'>");
 	html_txt(name);
@@ -373,6 +379,10 @@ 		html(delim);
 		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 @@ 		html(delim);
 		html("ignorews=1");
 		delim = "&amp;";
 	}
+	if (ctx.qry.follow) {
+		html(delim);
+		html("follow=1");
+	}
 	html("'>");
 	html_txt(name);
 	html("</a>");
@@ -469,7 +483,7 @@ 		cgit_log_link(name, title, class, ctx.qry.head,
 			      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 @@ 		cgit_refs_link("refs", NULL, hc("refs"), ctx.qry.head,
 			       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 @@ 	if (ctx.env.authenticated && ctx.qry.vpath) {
 		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 43d0fa619726543e58ce624fab59517437e43e7f..788b1bca5191e490a00e9a0b84e01fba9fa7a00e 100644
--- a/ui-shared.h
+++ b/ui-shared.h
@@ -31,7 +31,7 @@ 			    const char *rev, const char *path);
 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 bbc468ef7ec03395dfc04daa240e8c1330fcd41e..c8d24f653553c4116f5759dabb94b06710de4f06 100644
--- a/ui-tree.c
+++ b/ui-tree.c
@@ -166,7 +166,7 @@
 	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);