[PATCH 3/4] rebase: teach `reset_head()` to optionally skip the worktree

[Johannes Schindelin via GitGitGadget]

From: Johannes Schindelin <johannes.schinde...@gmx.de>

This is what the legacy (scripted) rebase does in
`move_to_original_branch`, and we will need this functionality in the
next commit.

Signed-off-by: Johannes Schindelin <johannes.schinde...@gmx.de>
---
 builtin/rebase.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/builtin/rebase.c b/builtin/rebase.c
index 768bea0da8..303175fdf1 100644
--- a/builtin/rebase.c
+++ b/builtin/rebase.c
@@ -337,6 +337,7 @@ static void add_var(struct strbuf *buf, const char *name, 
const char *value)
 
 #define RESET_HEAD_DETACH (1<<0)
 #define RESET_HEAD_HARD (1<<1)
+#define RESET_HEAD_REFS_ONLY (1<<2)
 
 static int reset_head(struct object_id *oid, const char *action,
                      const char *switch_to_branch, unsigned flags,
@@ -344,6 +345,7 @@ static int reset_head(struct object_id *oid, const char 
*action,
 {
        unsigned detach_head = flags & RESET_HEAD_DETACH;
        unsigned reset_hard = flags & RESET_HEAD_HARD;
+       unsigned refs_only = flags & RESET_HEAD_REFS_ONLY;
        struct object_id head_oid;
        struct tree_desc desc[2] = { { NULL }, { NULL } };
        struct lock_file lock = LOCK_INIT;
@@ -359,7 +361,7 @@ static int reset_head(struct object_id *oid, const char 
*action,
        if (switch_to_branch && !starts_with(switch_to_branch, "refs/"))
                BUG("Not a fully qualified branch: '%s'", switch_to_branch);
 
-       if (hold_locked_index(&lock, LOCK_REPORT_ON_ERROR) < 0) {
+       if (!refs_only && hold_locked_index(&lock, LOCK_REPORT_ON_ERROR) < 0) {
                ret = -1;
                goto leave_reset_head;
        }
@@ -372,6 +374,9 @@ static int reset_head(struct object_id *oid, const char 
*action,
        if (!oid)
                oid = &head_oid;
 
+       if (flags & RESET_HEAD_REFS_ONLY)
+               goto reset_head_refs;
+
        memset(&unpack_tree_opts, 0, sizeof(unpack_tree_opts));
        setup_unpack_trees_porcelain(&unpack_tree_opts, action);
        unpack_tree_opts.head_idx = 1;
@@ -412,6 +417,7 @@ static int reset_head(struct object_id *oid, const char 
*action,
                goto leave_reset_head;
        }
 
+reset_head_refs:
        reflog_action = getenv(GIT_REFLOG_ACTION_ENVIRONMENT);
        strbuf_addf(&msg, "%s: ", reflog_action ? reflog_action : "rebase");
        prefix_len = msg.len;
-- 
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