Re: [PATCH] branch: colorize branches checked out in a linked working tree the same way as the current branch is colorized

[Jeff King]

On Thu, Sep 27, 2018 at 08:13:13AM -0700, Nickolai Belakovski wrote:

> In order to more clearly display which branches are active, the output
> of git branch is modified to colorize branches checked out in any linked
> worktrees with the same color as the current branch.

I think the goal makes sense.

Do we want to limit this to git-branch, though? Ideally any output you
get from git-branch could be replicated with for-each-ref (or with
a custom "branch --format").

I.e., could we have a format in ref-filter that matches HEAD, but
returns a distinct symbol for a worktree HEAD? That would allow a few
things:

  - custom --formats for for-each-ref and branch could reuse the logic

  - we could show the symbol (in place of "*") even when color is not
    enabled

  - it should be much faster if there are a lot of worktrees; your patch
    does a linear if/else chain to look at each worktree, and it does it
    in the format-language, which is much slower than actual C. :)

Something like the patch below. I just picked "+" arbitrarily, but any
character would do (I avoided "*" just to make it visually distinct from
the current-worktree HEAD). I've left plugging this into git-branch's
default format as an exercise for the reader. ;)

---
diff --git a/ref-filter.c b/ref-filter.c
index e1bcb4ca8a..b17eefed0d 100644
--- a/ref-filter.c
+++ b/ref-filter.c
@@ -20,6 +20,7 @@
 #include "commit-slab.h"
 #include "commit-graph.h"
 #include "commit-reach.h"
+#include "worktree.h"
 
 static struct ref_msg {
        const char *gone;
@@ -114,6 +115,7 @@ static struct used_atom {
                } objectname;
                struct refname_atom refname;
                char *head;
+               struct string_list worktree_heads;
        } u;
 } *used_atom;
 static int used_atom_cnt, need_tagged, need_symref;
@@ -420,6 +422,29 @@ static int head_atom_parser(const struct ref_format 
*format, struct used_atom *a
        return 0;
 }
 
+static int worktree_head_atom_parser(const struct ref_format *format,
+                                    struct used_atom *atom,
+                                    const char *arg,
+                                    struct strbuf *unused_err)
+{
+       struct worktree **worktrees = get_worktrees(0);
+       int i;
+
+       string_list_init(&atom->u.worktree_heads, 1);
+
+       for (i = 0; worktrees[i]; i++) {
+               if (worktrees[i]->head_ref)
+                       string_list_append(&atom->u.worktree_heads,
+                                          worktrees[i]->head_ref);
+       }
+
+       string_list_sort(&atom->u.worktree_heads);
+
+       free_worktrees(worktrees);
+       return 0;
+
+}
+
 static struct {
        const char *name;
        info_source source;
@@ -460,6 +485,7 @@ static struct {
        { "symref", SOURCE_NONE, FIELD_STR, refname_atom_parser },
        { "flag", SOURCE_NONE },
        { "HEAD", SOURCE_NONE, FIELD_STR, head_atom_parser },
+       { "worktree", SOURCE_NONE, FIELD_STR, worktree_head_atom_parser },
        { "color", SOURCE_NONE, FIELD_STR, color_atom_parser },
        { "align", SOURCE_NONE, FIELD_STR, align_atom_parser },
        { "end", SOURCE_NONE },
@@ -1588,6 +1614,13 @@ static int populate_value(struct ref_array_item *ref, 
struct strbuf *err)
                        else
                                v->s = " ";
                        continue;
+               } else if (!strcmp(name, "worktree")) {
+                       if (string_list_has_string(&atom->u.worktree_heads,
+                                                  ref->refname))
+                               v->s = "+";
+                       else
+                               v->s = " ";
+                       continue;
                } else if (starts_with(name, "align")) {
                        v->handler = align_atom_handler;
                        v->s = "";