[PATCH 2/3] strbuf.h API users: don't hardcode 8192, use STRBUF_HINT_SIZE

["Ævar Arnfjörð Bjarmason" <avarab@gmail.com>]

Change a couple of users of strbuf_init() that pass a hint of 8192 to
pass STRBUF_HINT_SIZE instead.

Both of these hardcoded occurrences pre-date the use of the strbuf
API. See 5242bcbb638 (Use strbuf API in cache-tree.c, 2007-09-06) and
af6eb82262e (Use strbuf API in apply, blame, commit-tree and diff,
2007-09-06).

In both cases the exact choice of 8192 is rather arbitrary, e.g. for
commit buffers I think 1024 or 2048 would probably be a better
default (this commit message is getting this commit close to the
former, but I daresay it's already way above the average for git
commits).

In any case, if we ever tweak STRBUF_HINT_SIZE we'll probably do so on
the basis of some codease-wide performance tests, so replacing the
hardcoded value with STRBUF_HINT_SIZE should be safe, they're the same
now, and if we change STRBUF_HINT_SIZE in the future this is one of
the main codepaths we'll be testing.

Aside: It's unfortunate that we don't take a "hint" of "0" in
strbuf_init() to mean "default" and e.g. "-1" to mean the
strbuf_slopbuf (a in STRBUF_INIT). I considered adding that, or
splitting them up so you'd do strbuf_init(&buf) for the
strbuf_init(&buf, 0) case, or strbuf_init_alloc() for the
strbuf_init(&buf, N) case, where N > 0. But that would be a big change
across the codebase, so let's punt on that for now.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
---
 cache-tree.c | 2 +-
 commit.c     | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/cache-tree.c b/cache-tree.c
index 45e58666afc..d69f6d1c66f 100644
--- a/cache-tree.c
+++ b/cache-tree.c
@@ -335,7 +335,7 @@ static int update_one(struct cache_tree *it,
 	/*
 	 * Then write out the tree object for this level.
 	 */
-	strbuf_init(&buffer, 8192);
+	strbuf_init(&buffer, STRBUF_HINT_SIZE);
 
 	i = 0;
 	while (i < entries) {
diff --git a/commit.c b/commit.c
index 8ea55a447fa..b3aab46072a 100644
--- a/commit.c
+++ b/commit.c
@@ -1521,7 +1521,7 @@ int commit_tree_extended(const char *msg, size_t msg_len,
 	/* Not having i18n.commitencoding is the same as having utf-8 */
 	encoding_is_utf8 = is_encoding_utf8(git_commit_encoding);
 
-	strbuf_init(&buffer, 8192); /* should avoid reallocs for the headers */
+	strbuf_init(&buffer, STRBUF_HINT_SIZE); /* should avoid reallocs for the headers */
 	strbuf_addf(&buffer, "tree %s\n", oid_to_hex(tree));
 
 	/*
-- 
2.32.0.636.g43e71d69cff