[PATCH v2 0/9] Extending the shelf-life of "git describe" output

[PATCH v2 0/9] Extending the shelf-life of "git describe" output

[Junio C Hamano]

This is take 2.  The first round was $gmane/200165.

A major difference from v1 is the [PATCH 6/9].  The earlier approach
was to filter out candidates that match the given prefix for
additional criteria as they are found in the loop, but this round
tries to optimize for the common case of not having ambiguities.  We
postpone running additional test until we find the second object
that match the prefix (in other words, if there is only one object
that has the prefix, we do not apply the "we know this name refers
to a commit" hint, and let the caller deal with a non commit object,
just like the current code does).

Junio C Hamano (9):
  sha1_name.c: indentation fix
  sha1_name.c: clarify what "fake" is for in find_short_object_filename()
  sha1_name.c: rename "now" to "current"
  sha1_name.c: refactor find_short_packed_object()
  sha1_name.c: correct misnamed "canonical" and "res"
  sha1_name.c: restructure disambiguation of short names
  sha1_name.c: allow get_short_sha1() to take other flags
  sha1_name.c: teach get_short_sha1() a commit-only option
  sha1_name.c: get_describe_name() by definition groks only commits

 sha1_name.c | 282 +++++++++++++++++++++++++++++++++++++++---------------------
 1 file changed, 182 insertions(+), 100 deletions(-)

-- 
1.7.11.2.gd284367

[PATCH v2 1/9] sha1_name.c: indentation fix

[Junio C Hamano]

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 sha1_name.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sha1_name.c b/sha1_name.c
index 03ffc2c..5b0c845 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -103,10 +103,10 @@ static int find_short_packed_object(int len, const unsigned char *match, unsigne
 		}
 		if (first < num) {
 			const unsigned char *now, *next;
-		       now = nth_packed_object_sha1(p, first);
+			now = nth_packed_object_sha1(p, first);
 			if (match_sha(len, match, now)) {
 				next = nth_packed_object_sha1(p, first+1);
-			       if (!next|| !match_sha(len, match, next)) {
+				if (!next|| !match_sha(len, match, next)) {
 					/* unique within this pack */
 					if (!found) {
 						found_sha1 = now;
-- 
1.7.11.2.gd284367

[PATCH v2 2/9] sha1_name.c: clarify what "fake" is for in find_short_object_filename()

[Junio C Hamano]

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 sha1_name.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/sha1_name.c b/sha1_name.c
index 5b0c845..4cbca34 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -17,6 +17,13 @@ static int find_short_object_filename(int len, const char *name, unsigned char *
 	static struct alternate_object_database *fakeent;
 
 	if (!fakeent) {
+		/*
+		 * Create a "fake" alternate object database that
+		 * points to our own object database, to make it
+		 * easier to get a temporary working space in
+		 * alt->name/alt->base while iterating over the
+		 * object databases including our own.
+		 */
 		const char *objdir = get_object_directory();
 		int objdir_len = strlen(objdir);
 		int entlen = objdir_len + 43;
-- 
1.7.11.2.gd284367

[PATCH v2 3/9] sha1_name.c: rename "now" to "current"

[Junio C Hamano]

This variable points at the element we are currently looking at, and
does not have anything to do with the current time which the name
"now" implies.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 sha1_name.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/sha1_name.c b/sha1_name.c
index 4cbca34..5224f39 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -93,11 +93,11 @@ static int find_short_packed_object(int len, const unsigned char *match, unsigne
 		last = num;
 		while (first < last) {
 			uint32_t mid = (first + last) / 2;
-			const unsigned char *now;
+			const unsigned char *current;
 			int cmp;
 
-			now = nth_packed_object_sha1(p, mid);
-			cmp = hashcmp(match, now);
+			current = nth_packed_object_sha1(p, mid);
+			cmp = hashcmp(match, current);
 			if (!cmp) {
 				first = mid;
 				break;
@@ -109,17 +109,17 @@ static int find_short_packed_object(int len, const unsigned char *match, unsigne
 			last = mid;
 		}
 		if (first < num) {
-			const unsigned char *now, *next;
-			now = nth_packed_object_sha1(p, first);
-			if (match_sha(len, match, now)) {
+			const unsigned char *current, *next;
+			current = nth_packed_object_sha1(p, first);
+			if (match_sha(len, match, current)) {
 				next = nth_packed_object_sha1(p, first+1);
 				if (!next|| !match_sha(len, match, next)) {
 					/* unique within this pack */
 					if (!found) {
-						found_sha1 = now;
+						found_sha1 = current;
 						found++;
 					}
-					else if (hashcmp(found_sha1, now)) {
+					else if (hashcmp(found_sha1, current)) {
 						found = 2;
 						break;
 					}
-- 
1.7.11.2.gd284367

[PATCH v2 4/9] sha1_name.c: refactor find_short_packed_object()

[Junio C Hamano]

Extract the logic to find object(s) that match a given prefix inside
a single pack into a separate helper function, and give it a bit more
comment.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 sha1_name.c | 103 +++++++++++++++++++++++++++++++++---------------------------
 1 file changed, 56 insertions(+), 47 deletions(-)

diff --git a/sha1_name.c b/sha1_name.c
index 5224f39..e03992c 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -78,6 +78,59 @@ static int match_sha(unsigned len, const unsigned char *a, const unsigned char *
 	return 1;
 }
 
+static int unique_in_pack(int len,
+			  const unsigned char *match,
+			  struct packed_git *p,
+			  const unsigned char **found_sha1,
+			  int seen_so_far)
+{
+	uint32_t num, last, i, first = 0;
+	const unsigned char *current = NULL;
+
+	open_pack_index(p);
+	num = p->num_objects;
+	last = num;
+	while (first < last) {
+		uint32_t mid = (first + last) / 2;
+		const unsigned char *current;
+		int cmp;
+
+		current = nth_packed_object_sha1(p, mid);
+		cmp = hashcmp(match, current);
+		if (!cmp) {
+			first = mid;
+			break;
+		}
+		if (cmp > 0) {
+			first = mid+1;
+			continue;
+		}
+		last = mid;
+	}
+
+	/*
+	 * At this point, "first" is the location of the lowest object
+	 * with an object name that could match "match".  See if we have
+	 * 0, 1 or more objects that actually match(es).
+	 */
+	for (i = first; i < num; i++) {
+		current = nth_packed_object_sha1(p, first);
+		if (!match_sha(len, match, current))
+			break;
+
+		/* current matches */
+		if (!seen_so_far) {
+			*found_sha1 = current;
+			seen_so_far++;
+		} else if (seen_so_far) {
+			/* is it the same as the one previously found elsewhere? */
+			if (hashcmp(*found_sha1, current))
+				return 2; /* definitely not unique */
+		}
+	}
+	return seen_so_far;
+}
+
 static int find_short_packed_object(int len, const unsigned char *match, unsigned char *sha1)
 {
 	struct packed_git *p;
@@ -85,53 +138,9 @@ static int find_short_packed_object(int len, const unsigned char *match, unsigne
 	int found = 0;
 
 	prepare_packed_git();
-	for (p = packed_git; p && found < 2; p = p->next) {
-		uint32_t num, last;
-		uint32_t first = 0;
-		open_pack_index(p);
-		num = p->num_objects;
-		last = num;
-		while (first < last) {
-			uint32_t mid = (first + last) / 2;
-			const unsigned char *current;
-			int cmp;
-
-			current = nth_packed_object_sha1(p, mid);
-			cmp = hashcmp(match, current);
-			if (!cmp) {
-				first = mid;
-				break;
-			}
-			if (cmp > 0) {
-				first = mid+1;
-				continue;
-			}
-			last = mid;
-		}
-		if (first < num) {
-			const unsigned char *current, *next;
-			current = nth_packed_object_sha1(p, first);
-			if (match_sha(len, match, current)) {
-				next = nth_packed_object_sha1(p, first+1);
-				if (!next|| !match_sha(len, match, next)) {
-					/* unique within this pack */
-					if (!found) {
-						found_sha1 = current;
-						found++;
-					}
-					else if (hashcmp(found_sha1, current)) {
-						found = 2;
-						break;
-					}
-				}
-				else {
-					/* not even unique within this pack */
-					found = 2;
-					break;
-				}
-			}
-		}
-	}
+	for (p = packed_git; p && found < 2; p = p->next)
+		found = unique_in_pack(len, match, p, &found_sha1, found);
+
 	if (found == 1)
 		hashcpy(sha1, found_sha1);
 	return found;
-- 
1.7.11.2.gd284367

[PATCH v2 5/9] sha1_name.c: correct misnamed "canonical" and "res"

[Junio C Hamano]

These are hexadecimal and binary representation of the short object
name given to the callchain as its input.  Rename them with _pfx
suffix to make it clear they are prefixes, and call them hex and bin
respectively.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 sha1_name.c | 44 ++++++++++++++++++++++----------------------
 1 file changed, 22 insertions(+), 22 deletions(-)

diff --git a/sha1_name.c b/sha1_name.c
index e03992c..7062f72 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -9,7 +9,7 @@
 
 static int get_sha1_oneline(const char *, unsigned char *, struct commit_list *);
 
-static int find_short_object_filename(int len, const char *name, unsigned char *sha1)
+static int find_short_object_filename(int len, const char *hex_pfx, unsigned char *sha1)
 {
 	struct alternate_object_database *alt;
 	char hex[40];
@@ -34,18 +34,18 @@ static int find_short_object_filename(int len, const char *name, unsigned char *
 	}
 	fakeent->next = alt_odb_list;
 
-	sprintf(hex, "%.2s", name);
+	sprintf(hex, "%.2s", hex_pfx);
 	for (alt = fakeent; alt && found < 2; alt = alt->next) {
 		struct dirent *de;
 		DIR *dir;
-		sprintf(alt->name, "%.2s/", name);
+		sprintf(alt->name, "%.2s/", hex_pfx);
 		dir = opendir(alt->base);
 		if (!dir)
 			continue;
 		while ((de = readdir(dir)) != NULL) {
 			if (strlen(de->d_name) != 38)
 				continue;
-			if (memcmp(de->d_name, name + 2, len - 2))
+			if (memcmp(de->d_name, hex_pfx + 2, len - 2))
 				continue;
 			if (!found) {
 				memcpy(hex + 2, de->d_name, 38);
@@ -79,7 +79,7 @@ static int match_sha(unsigned len, const unsigned char *a, const unsigned char *
 }
 
 static int unique_in_pack(int len,
-			  const unsigned char *match,
+			  const unsigned char *bin_pfx,
 			  struct packed_git *p,
 			  const unsigned char **found_sha1,
 			  int seen_so_far)
@@ -96,7 +96,7 @@ static int unique_in_pack(int len,
 		int cmp;
 
 		current = nth_packed_object_sha1(p, mid);
-		cmp = hashcmp(match, current);
+		cmp = hashcmp(bin_pfx, current);
 		if (!cmp) {
 			first = mid;
 			break;
@@ -110,12 +110,12 @@ static int unique_in_pack(int len,
 
 	/*
 	 * At this point, "first" is the location of the lowest object
-	 * with an object name that could match "match".  See if we have
+	 * with an object name that could match "bin_pfx".  See if we have
 	 * 0, 1 or more objects that actually match(es).
 	 */
 	for (i = first; i < num; i++) {
 		current = nth_packed_object_sha1(p, first);
-		if (!match_sha(len, match, current))
+		if (!match_sha(len, bin_pfx, current))
 			break;
 
 		/* current matches */
@@ -131,7 +131,7 @@ static int unique_in_pack(int len,
 	return seen_so_far;
 }
 
-static int find_short_packed_object(int len, const unsigned char *match, unsigned char *sha1)
+static int find_short_packed_object(int len, const unsigned char *bin_pfx, unsigned char *sha1)
 {
 	struct packed_git *p;
 	const unsigned char *found_sha1 = NULL;
@@ -139,7 +139,7 @@ static int find_short_packed_object(int len, const unsigned char *match, unsigne
 
 	prepare_packed_git();
 	for (p = packed_git; p && found < 2; p = p->next)
-		found = unique_in_pack(len, match, p, &found_sha1, found);
+		found = unique_in_pack(len, bin_pfx, p, &found_sha1, found);
 
 	if (found == 1)
 		hashcpy(sha1, found_sha1);
@@ -149,15 +149,15 @@ static int find_short_packed_object(int len, const unsigned char *match, unsigne
 #define SHORT_NAME_NOT_FOUND (-1)
 #define SHORT_NAME_AMBIGUOUS (-2)
 
-static int find_unique_short_object(int len, char *canonical,
-				    unsigned char *res, unsigned char *sha1)
+static int find_unique_short_object(int len, char *hex_pfx,
+				    unsigned char *bin_pfx, unsigned char *sha1)
 {
 	int has_unpacked, has_packed;
 	unsigned char unpacked_sha1[20], packed_sha1[20];
 
 	prepare_alt_odb();
-	has_unpacked = find_short_object_filename(len, canonical, unpacked_sha1);
-	has_packed = find_short_packed_object(len, res, packed_sha1);
+	has_unpacked = find_short_object_filename(len, hex_pfx, unpacked_sha1);
+	has_packed = find_short_packed_object(len, bin_pfx, packed_sha1);
 	if (!has_unpacked && !has_packed)
 		return SHORT_NAME_NOT_FOUND;
 	if (1 < has_unpacked || 1 < has_packed)
@@ -177,13 +177,13 @@ static int get_short_sha1(const char *name, int len, unsigned char *sha1,
 			  int quietly)
 {
 	int i, status;
-	char canonical[40];
-	unsigned char res[20];
+	char hex_pfx[40];
+	unsigned char bin_pfx[20];
 
 	if (len < MINIMUM_ABBREV || len > 40)
 		return -1;
-	hashclr(res);
-	memset(canonical, 'x', 40);
+	hashclr(bin_pfx);
+	memset(hex_pfx, 'x', 40);
 	for (i = 0; i < len ;i++) {
 		unsigned char c = name[i];
 		unsigned char val;
@@ -197,15 +197,15 @@ static int get_short_sha1(const char *name, int len, unsigned char *sha1,
 		}
 		else
 			return -1;
-		canonical[i] = c;
+		hex_pfx[i] = c;
 		if (!(i & 1))
 			val <<= 4;
-		res[i >> 1] |= val;
+		bin_pfx[i >> 1] |= val;
 	}
 
-	status = find_unique_short_object(i, canonical, res, sha1);
+	status = find_unique_short_object(i, hex_pfx, bin_pfx, sha1);
 	if (!quietly && (status == SHORT_NAME_AMBIGUOUS))
-		return error("short SHA1 %.*s is ambiguous.", len, canonical);
+		return error("short SHA1 %.*s is ambiguous.", len, hex_pfx);
 	return status;
 }
 
-- 
1.7.11.2.gd284367

[PATCH v2 6/9] sha1_name.c: restructure disambiguation of short names

[Junio C Hamano]

We try to find zero, one or more matches from loose objects and
packed objects independently and then decide if the given short
object name is unique across them.

Instead, introduce a "struct disambiguate_state" that keeps track of
what we have found so far, that can be one of:

 - We have seen one object that _could_ be what we are looking for;
 - We have also checked that object for additional constraints (if any),
   and found that the object satisfies it;
 - We have also checked that object for additional constraints (if any),
   and found that the object does not satisfy it; or
 - We have seen more than one objects that satisfy the constraints.

and pass it to the enumeration functions for loose and packed
objects.  The disambiguation state can optionally take a callback
function that takes a candidate object name and reports if the
object satisifies additional criteria (e.g. when the caller knows
that the short name must refer to a commit, this mechanism can be
used to check the type of the given object).

Compared to the earlier attempt, this round avoids the optional
check if there is only one candidate that matches the short name in
the first place.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 sha1_name.c | 172 +++++++++++++++++++++++++++++++++++++++---------------------
 1 file changed, 112 insertions(+), 60 deletions(-)

diff --git a/sha1_name.c b/sha1_name.c
index 7062f72..852d5c2 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -9,11 +9,67 @@
 
 static int get_sha1_oneline(const char *, unsigned char *, struct commit_list *);
 
-static int find_short_object_filename(int len, const char *hex_pfx, unsigned char *sha1)
+typedef int (*disambiguate_hint_fn)(const unsigned char *, void *);
+
+struct disambiguate_state {
+	disambiguate_hint_fn fn;
+	void *cb_data;
+	unsigned char candidate[20];
+	unsigned candidate_exists:1;
+	unsigned candidate_checked:1;
+	unsigned candidate_ok:1;
+	unsigned disambiguate_fn_used:1;
+	unsigned ambiguous:1;
+};
+
+static void update_candidates(struct disambiguate_state *ds, const unsigned char *current)
+{
+	if (!ds->candidate_exists) {
+		/* this is the first candidate */
+		hashcpy(ds->candidate, current);
+		ds->candidate_exists = 1;
+		return;
+	} else if (!hashcmp(ds->candidate, current)) {
+		/* the same as what we already have seen */
+		return;
+	}
+
+	if (!ds->fn) {
+		/* cannot disambiguate between ds->candidate and current */
+		ds->ambiguous = 1;
+		return;
+	}
+
+	if (!ds->candidate_checked) {
+		ds->candidate_ok = ds->fn(ds->candidate, ds->cb_data);
+		ds->disambiguate_fn_used = 1;
+		ds->candidate_checked = 1;
+	}
+
+	if (!ds->candidate_ok) {
+		/* discard the candidate; we know it does not satisify fn */
+		hashcpy(ds->candidate, current);
+		ds->candidate_checked = 0;
+		return;
+	}
+
+	/* if we reach this point, we know ds->candidate satisfies fn */
+	if (ds->fn(current, ds->cb_data)) {
+		/*
+		 * if both current and candidate satisfy fn, we cannot
+		 * disambiguate.
+		 */
+		ds->candidate_ok = 0;
+		ds->ambiguous = 1;
+	}
+
+	/* otherwise, current can be discarded and candidate is still good */
+}
+
+static void find_short_object_filename(int len, const char *hex_pfx, struct disambiguate_state *ds)
 {
 	struct alternate_object_database *alt;
 	char hex[40];
-	int found = 0;
 	static struct alternate_object_database *fakeent;
 
 	if (!fakeent) {
@@ -35,32 +91,27 @@ static int find_short_object_filename(int len, const char *hex_pfx, unsigned cha
 	fakeent->next = alt_odb_list;
 
 	sprintf(hex, "%.2s", hex_pfx);
-	for (alt = fakeent; alt && found < 2; alt = alt->next) {
+	for (alt = fakeent; alt && !ds->ambiguous; alt = alt->next) {
 		struct dirent *de;
 		DIR *dir;
 		sprintf(alt->name, "%.2s/", hex_pfx);
 		dir = opendir(alt->base);
 		if (!dir)
 			continue;
-		while ((de = readdir(dir)) != NULL) {
+
+		while (!ds->ambiguous && (de = readdir(dir)) != NULL) {
+			unsigned char sha1[20];
+
 			if (strlen(de->d_name) != 38)
 				continue;
 			if (memcmp(de->d_name, hex_pfx + 2, len - 2))
 				continue;
-			if (!found) {
-				memcpy(hex + 2, de->d_name, 38);
-				found++;
-			}
-			else if (memcmp(hex + 2, de->d_name, 38)) {
-				found = 2;
-				break;
-			}
+			memcpy(hex + 2, de->d_name, 38);
+			if (!get_sha1_hex(hex, sha1))
+				update_candidates(ds, sha1);
 		}
 		closedir(dir);
 	}
-	if (found == 1)
-		return get_sha1_hex(hex, sha1) == 0;
-	return found;
 }
 
 static int match_sha(unsigned len, const unsigned char *a, const unsigned char *b)
@@ -78,11 +129,10 @@ static int match_sha(unsigned len, const unsigned char *a, const unsigned char *
 	return 1;
 }
 
-static int unique_in_pack(int len,
+static void unique_in_pack(int len,
 			  const unsigned char *bin_pfx,
-			  struct packed_git *p,
-			  const unsigned char **found_sha1,
-			  int seen_so_far)
+			   struct packed_git *p,
+			   struct disambiguate_state *ds)
 {
 	uint32_t num, last, i, first = 0;
 	const unsigned char *current = NULL;
@@ -113,63 +163,58 @@ static int unique_in_pack(int len,
 	 * with an object name that could match "bin_pfx".  See if we have
 	 * 0, 1 or more objects that actually match(es).
 	 */
-	for (i = first; i < num; i++) {
-		current = nth_packed_object_sha1(p, first);
+	for (i = first; i < num && !ds->ambiguous; i++) {
+		current = nth_packed_object_sha1(p, i);
 		if (!match_sha(len, bin_pfx, current))
 			break;
-
-		/* current matches */
-		if (!seen_so_far) {
-			*found_sha1 = current;
-			seen_so_far++;
-		} else if (seen_so_far) {
-			/* is it the same as the one previously found elsewhere? */
-			if (hashcmp(*found_sha1, current))
-				return 2; /* definitely not unique */
-		}
+		update_candidates(ds, current);
 	}
-	return seen_so_far;
 }
 
-static int find_short_packed_object(int len, const unsigned char *bin_pfx, unsigned char *sha1)
+static void find_short_packed_object(int len, const unsigned char *bin_pfx,
+				     struct disambiguate_state *ds)
 {
 	struct packed_git *p;
-	const unsigned char *found_sha1 = NULL;
-	int found = 0;
 
 	prepare_packed_git();
-	for (p = packed_git; p && found < 2; p = p->next)
-		found = unique_in_pack(len, bin_pfx, p, &found_sha1, found);
-
-	if (found == 1)
-		hashcpy(sha1, found_sha1);
-	return found;
+	for (p = packed_git; p && !ds->ambiguous; p = p->next)
+		unique_in_pack(len, bin_pfx, p, ds);
 }
 
 #define SHORT_NAME_NOT_FOUND (-1)
 #define SHORT_NAME_AMBIGUOUS (-2)
 
-static int find_unique_short_object(int len, char *hex_pfx,
-				    unsigned char *bin_pfx, unsigned char *sha1)
+static int finish_object_disambiguation(struct disambiguate_state *ds,
+					unsigned char *sha1)
 {
-	int has_unpacked, has_packed;
-	unsigned char unpacked_sha1[20], packed_sha1[20];
+	if (ds->ambiguous)
+		return SHORT_NAME_AMBIGUOUS;
 
-	prepare_alt_odb();
-	has_unpacked = find_short_object_filename(len, hex_pfx, unpacked_sha1);
-	has_packed = find_short_packed_object(len, bin_pfx, packed_sha1);
-	if (!has_unpacked && !has_packed)
+	if (!ds->candidate_exists)
 		return SHORT_NAME_NOT_FOUND;
-	if (1 < has_unpacked || 1 < has_packed)
-		return SHORT_NAME_AMBIGUOUS;
-	if (has_unpacked != has_packed) {
-		hashcpy(sha1, (has_packed ? packed_sha1 : unpacked_sha1));
-		return 0;
-	}
-	/* Both have unique ones -- do they match? */
-	if (hashcmp(packed_sha1, unpacked_sha1))
-		return SHORT_NAME_AMBIGUOUS;
-	hashcpy(sha1, packed_sha1);
+
+	if (!ds->candidate_checked)
+		/*
+		 * If this is the only candidate, there is no point
+		 * calling the disambiguation hint callback.
+		 *
+		 * On the other hand, if the current candidate
+		 * replaced an earlier candidate that did _not_ pass
+		 * the disambiguation hint callback, then we do have
+		 * more than one objects that match the short name
+		 * given, so we should make sure this one matches;
+		 * otherwise, if we discovered this one and the one
+		 * that we previously discarded in the reverse order,
+		 * we would end up showing different results in the
+		 * same repository!
+		 */
+		ds->candidate_ok = (!ds->disambiguate_fn_used ||
+				    ds->fn(ds->candidate, ds->cb_data));
+
+	if (!ds->candidate_ok)
+		return SHORT_NAME_NOT_FOUND;
+
+	hashcpy(sha1, ds->candidate);
 	return 0;
 }
 
@@ -179,6 +224,7 @@ static int get_short_sha1(const char *name, int len, unsigned char *sha1,
 	int i, status;
 	char hex_pfx[40];
 	unsigned char bin_pfx[20];
+	struct disambiguate_state ds;
 
 	if (len < MINIMUM_ABBREV || len > 40)
 		return -1;
@@ -203,7 +249,13 @@ static int get_short_sha1(const char *name, int len, unsigned char *sha1,
 		bin_pfx[i >> 1] |= val;
 	}
 
-	status = find_unique_short_object(i, hex_pfx, bin_pfx, sha1);
+	prepare_alt_odb();
+
+	memset(&ds, 0, sizeof(ds));
+	find_short_object_filename(len, hex_pfx, &ds);
+	find_short_packed_object(len, bin_pfx, &ds);
+	status = finish_object_disambiguation(&ds, sha1);
+
 	if (!quietly && (status == SHORT_NAME_AMBIGUOUS))
 		return error("short SHA1 %.*s is ambiguous.", len, hex_pfx);
 	return status;
-- 
1.7.11.2.gd284367

[PATCH v2 7/9] sha1_name.c: allow get_short_sha1() to take other flags

[Junio C Hamano]

Instead of a separate "int quietly" argument, make it take "unsigned flags"
so that we can pass other options to it.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 sha1_name.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/sha1_name.c b/sha1_name.c
index 852d5c2..7cca7d9 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -218,13 +218,16 @@ static int finish_object_disambiguation(struct disambiguate_state *ds,
 	return 0;
 }
 
+#define GET_SHORT_QUIETLY 01
+
 static int get_short_sha1(const char *name, int len, unsigned char *sha1,
-			  int quietly)
+			  unsigned flags)
 {
 	int i, status;
 	char hex_pfx[40];
 	unsigned char bin_pfx[20];
 	struct disambiguate_state ds;
+	int quietly = !!(flags & GET_SHORT_QUIETLY);
 
 	if (len < MINIMUM_ABBREV || len > 40)
 		return -1;
@@ -272,7 +275,7 @@ const char *find_unique_abbrev(const unsigned char *sha1, int len)
 		return hex;
 	while (len < 40) {
 		unsigned char sha1_ret[20];
-		status = get_short_sha1(hex, len, sha1_ret, 1);
+		status = get_short_sha1(hex, len, sha1_ret, GET_SHORT_QUIETLY);
 		if (exists
 		    ? !status
 		    : status == SHORT_NAME_NOT_FOUND) {
@@ -603,7 +606,7 @@ static int get_describe_name(const char *name, int len, unsigned char *sha1)
 			if (ch == 'g' && cp[-1] == '-') {
 				cp++;
 				len -= cp - name;
-				return get_short_sha1(cp, len, sha1, 1);
+				return get_short_sha1(cp, len, sha1, GET_SHORT_QUIETLY);
 			}
 		}
 	}
-- 
1.7.11.2.gd284367

[PATCH v2 8/9] sha1_name.c: teach get_short_sha1() a commit-only option

[Junio C Hamano]

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 sha1_name.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/sha1_name.c b/sha1_name.c
index 7cca7d9..58dbbe2 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -219,6 +219,13 @@ static int finish_object_disambiguation(struct disambiguate_state *ds,
 }
 
 #define GET_SHORT_QUIETLY 01
+#define GET_SHORT_COMMIT_ONLY 02
+
+static int disambiguate_commit_only(const unsigned char *sha1, void *cb_data_unused)
+{
+	int kind = sha1_object_info(sha1, NULL);
+	return kind == OBJ_COMMIT;
+}
 
 static int get_short_sha1(const char *name, int len, unsigned char *sha1,
 			  unsigned flags)
@@ -255,6 +262,9 @@ static int get_short_sha1(const char *name, int len, unsigned char *sha1,
 	prepare_alt_odb();
 
 	memset(&ds, 0, sizeof(ds));
+	if (flags & GET_SHORT_COMMIT_ONLY)
+		ds.fn = disambiguate_commit_only;
+
 	find_short_object_filename(len, hex_pfx, &ds);
 	find_short_packed_object(len, bin_pfx, &ds);
 	status = finish_object_disambiguation(&ds, sha1);
-- 
1.7.11.2.gd284367

[PATCH v2 9/9] sha1_name.c: get_describe_name() by definition groks only commits

[Junio C Hamano]

Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 sha1_name.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/sha1_name.c b/sha1_name.c
index 58dbbe2..15e97eb 100644
--- a/sha1_name.c
+++ b/sha1_name.c
@@ -606,6 +606,7 @@ static int peel_onion(const char *name, int len, unsigned char *sha1)
 static int get_describe_name(const char *name, int len, unsigned char *sha1)
 {
 	const char *cp;
+	unsigned flags = GET_SHORT_QUIETLY | GET_SHORT_COMMIT_ONLY;
 
 	for (cp = name + len - 1; name + 2 <= cp; cp--) {
 		char ch = *cp;
@@ -616,7 +617,7 @@ static int get_describe_name(const char *name, int len, unsigned char *sha1)
 			if (ch == 'g' && cp[-1] == '-') {
 				cp++;
 				len -= cp - name;
-				return get_short_sha1(cp, len, sha1, GET_SHORT_QUIETLY);
+				return get_short_sha1(cp, len, sha1, flags);
 			}
 		}
 	}
-- 
1.7.11.2.gd284367

Re: [PATCH v2 9/9] sha1_name.c: get_describe_name() by definition groks only commits

[Erik Faye-Lund]

On Thu, Jun 21, 2012 at 8:35 AM, Junio C Hamano <gitster@pobox.com> wrote:
> Signed-off-by: Junio C Hamano <gitster@pobox.com>
> ---
>  sha1_name.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/sha1_name.c b/sha1_name.c
> index 58dbbe2..15e97eb 100644
> --- a/sha1_name.c
> +++ b/sha1_name.c
> @@ -606,6 +606,7 @@ static int peel_onion(const char *name, int len, unsigned char *sha1)
>  static int get_describe_name(const char *name, int len, unsigned char *sha1)
>  {
>        const char *cp;
> +       unsigned flags = GET_SHORT_QUIETLY | GET_SHORT_COMMIT_ONLY;
>
>        for (cp = name + len - 1; name + 2 <= cp; cp--) {
>                char ch = *cp;
> @@ -616,7 +617,7 @@ static int get_describe_name(const char *name, int len, unsigned char *sha1)
>                        if (ch == 'g' && cp[-1] == '-') {
>                                cp++;
>                                len -= cp - name;
> -                               return get_short_sha1(cp, len, sha1, GET_SHORT_QUIETLY);
> +                               return get_short_sha1(cp, len, sha1, flags);

Is there a reason why you chose to put the definition in the
root-scope of the function? There's an excellent opportunity just a
few lines above the only place it's used, and I suspect it would
increase readability to put it there...

Re: [PATCH v2 9/9] sha1_name.c: get_describe_name() by definition groks only commits

[Junio C Hamano]

Erik Faye-Lund <kusmabite@gmail.com> writes:

> On Thu, Jun 21, 2012 at 8:35 AM, Junio C Hamano <gitster@pobox.com> wrote:
>> Signed-off-by: Junio C Hamano <gitster@pobox.com>
>> ---
>>  sha1_name.c | 3 ++-
>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/sha1_name.c b/sha1_name.c
>> index 58dbbe2..15e97eb 100644
>> --- a/sha1_name.c
>> +++ b/sha1_name.c
>> @@ -606,6 +606,7 @@ static int peel_onion(const char *name, int len, unsigned char *sha1)
>>  static int get_describe_name(const char *name, int len, unsigned char *sha1)
>>  {
>>        const char *cp;
>> +       unsigned flags = GET_SHORT_QUIETLY | GET_SHORT_COMMIT_ONLY;
>>
>>        for (cp = name + len - 1; name + 2 <= cp; cp--) {
>>                char ch = *cp;
>> @@ -616,7 +617,7 @@ static int get_describe_name(const char *name, int len, unsigned char *sha1)
>>                        if (ch == 'g' && cp[-1] == '-') {
>>                                cp++;
>>                                len -= cp - name;
>> -                               return get_short_sha1(cp, len, sha1, GET_SHORT_QUIETLY);
>> +                               return get_short_sha1(cp, len, sha1, flags);
>
> Is there a reason why you chose to put the definition in the
> root-scope of the function?

Mostly because it never changes inside the loop.  "unsigned const
flags" upfront might have even been a better option, though.

A less important reason is it would make the resulting file wider,
not narrower, than the original.