[PATCH v4 3/9] Add a function to update HEAD after creating a commit

[Phillip Wood]

From: Phillip Wood <phillip.w...@dunelm.org.uk>

Add update_head_with_reflog() based on the code that updates HEAD
after committing in builtin/commit.c that can be called by 'git
commit' and other commands.

Signed-off-by: Phillip Wood <phillip.w...@dunelm.org.uk>
---

Notes:
    changes since v2:
     - updated commit message to reflect the change in function name
     - style fixes
    
    changes since v1:
     - rename update_head() to update_head_with_reflog()

 builtin/commit.c | 20 ++------------------
 sequencer.c      | 39 ++++++++++++++++++++++++++++++++++++++-
 sequencer.h      |  4 ++++
 3 files changed, 44 insertions(+), 19 deletions(-)

diff --git a/builtin/commit.c b/builtin/commit.c
index 
d958c2eb2adc9a29dab29340ce9b56daea41fecd..eb144556bf37b7bf357bd976b94305171b4fd159
 100644
--- a/builtin/commit.c
+++ b/builtin/commit.c
@@ -1610,13 +1610,11 @@ int cmd_commit(int argc, const char **argv, const char 
*prefix)
        struct strbuf sb = STRBUF_INIT;
        struct strbuf author_ident = STRBUF_INIT;
        const char *index_file, *reflog_msg;
-       char *nl;
        struct object_id oid;
        struct commit_list *parents = NULL;
        struct stat statbuf;
        struct commit *current_head = NULL;
        struct commit_extra_header *extra = NULL;
-       struct ref_transaction *transaction;
        struct strbuf err = STRBUF_INIT;
 
        if (argc == 2 && !strcmp(argv[1], "-h"))
@@ -1739,25 +1737,11 @@ int cmd_commit(int argc, const char **argv, const char 
*prefix)
        strbuf_release(&author_ident);
        free_commit_extra_headers(extra);
 
-       nl = strchr(sb.buf, '\n');
-       if (nl)
-               strbuf_setlen(&sb, nl + 1 - sb.buf);
-       else
-               strbuf_addch(&sb, '\n');
-       strbuf_insert(&sb, 0, reflog_msg, strlen(reflog_msg));
-       strbuf_insert(&sb, strlen(reflog_msg), ": ", 2);
-
-       transaction = ref_transaction_begin(&err);
-       if (!transaction ||
-           ref_transaction_update(transaction, "HEAD", &oid,
-                                  current_head
-                                  ? &current_head->object.oid : &null_oid,
-                                  0, sb.buf, &err) ||
-           ref_transaction_commit(transaction, &err)) {
+       if (update_head_with_reflog(current_head, &oid, reflog_msg, &sb,
+                                   &err)) {
                rollback_index_files();
                die("%s", err.buf);
        }
-       ref_transaction_free(transaction);
 
        unlink(git_path_cherry_pick_head());
        unlink(git_path_revert_head());
diff --git a/sequencer.c b/sequencer.c
index 
36e03d041f32bcc0fdd1fddebb33b23c7e4d8a70..ef262980c5255d90ee023c0b29c6c1c628b3c7d2
 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -1,10 +1,10 @@
 #include "cache.h"
 #include "config.h"
 #include "lockfile.h"
-#include "sequencer.h"
 #include "dir.h"
 #include "object.h"
 #include "commit.h"
+#include "sequencer.h"
 #include "tag.h"
 #include "run-command.h"
 #include "exec_cmd.h"
@@ -752,6 +752,43 @@ int template_untouched(const struct strbuf *sb, const char 
*template_file,
        return rest_is_empty(sb, start - sb->buf);
 }
 
+int update_head_with_reflog(const struct commit *old_head,
+                           const struct object_id *new_head,
+                           const char *action, const struct strbuf *msg,
+                           struct strbuf *err)
+{
+       struct ref_transaction *transaction;
+       struct strbuf sb = STRBUF_INIT;
+       const char *nl;
+       int ret = 0;
+
+       if (action) {
+               strbuf_addstr(&sb, action);
+               strbuf_addstr(&sb, ": ");
+       }
+
+       nl = strchr(msg->buf, '\n');
+       if (nl) {
+               strbuf_add(&sb, msg->buf, nl + 1 - msg->buf);
+       } else {
+               strbuf_addbuf(&sb, msg);
+               strbuf_addch(&sb, '\n');
+       }
+
+       transaction = ref_transaction_begin(err);
+       if (!transaction ||
+           ref_transaction_update(transaction, "HEAD", new_head,
+                                  old_head ? &old_head->object.oid : &null_oid,
+                                  0, sb.buf, err) ||
+           ref_transaction_commit(transaction, err)) {
+               ret = -1;
+       }
+       ref_transaction_free(transaction);
+       strbuf_release(&sb);
+
+       return ret;
+}
+
 static int is_original_commit_empty(struct commit *commit)
 {
        const struct object_id *ptree_oid;
diff --git a/sequencer.h b/sequencer.h
index 
82e57713a2940c5d65ccac013c3f42c55cc12baf..81a2098e900f0aca30e45ed7f19ae4bf3ce682f0
 100644
--- a/sequencer.h
+++ b/sequencer.h
@@ -69,4 +69,8 @@ int message_is_empty(const struct strbuf *sb,
                     enum commit_msg_cleanup_mode cleanup_mode);
 int template_untouched(const struct strbuf *sb, const char *template_file,
                       enum commit_msg_cleanup_mode cleanup_mode);
+int update_head_with_reflog(const struct commit *old_head,
+                           const struct object_id *new_head,
+                           const char *action, const struct strbuf *msg,
+                           struct strbuf *err);
 #endif
-- 
2.15.0