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authorJunio C Hamano <junkio@cox.net>2007-01-30 01:36:22 (GMT)
committerJunio C Hamano <junkio@cox.net>2007-01-30 03:41:21 (GMT)
commit1732a1fd942f00b9a77a47acc09df0cd62c770bd (patch)
treeb788c756c211dda4a500e6fd3c132f7d543e5d9e /builtin-blame.c
parentb4dfefe00f7035140b7a10e855a665c1347cacd6 (diff)
downloadgit-1732a1fd942f00b9a77a47acc09df0cd62c770bd.zip
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git-blame: somewhat better commenting.
Signed-off-by: Junio C Hamano <junkio@cox.net>
Diffstat (limited to 'builtin-blame.c')
-rw-r--r--builtin-blame.c293
1 files changed, 255 insertions, 38 deletions
diff --git a/builtin-blame.c b/builtin-blame.c
index 02bda5e..3033e9b 100644
--- a/builtin-blame.c
+++ b/builtin-blame.c
@@ -77,6 +77,10 @@ struct origin {
char path[FLEX_ARRAY];
};
+/*
+ * Given an origin, prepare mmfile_t structure to be used by the
+ * diff machinery
+ */
static char *fill_origin_blob(struct origin *o, mmfile_t *file)
{
if (!o->file.ptr) {
@@ -91,6 +95,10 @@ static char *fill_origin_blob(struct origin *o, mmfile_t *file)
return file->ptr;
}
+/*
+ * Origin is refcounted and usually we keep the blob contents to be
+ * reused.
+ */
static inline struct origin *origin_incref(struct origin *o)
{
if (o)
@@ -108,6 +116,11 @@ static void origin_decref(struct origin *o)
}
}
+/*
+ * Each group of lines is described by a blame_entry; it can be split
+ * as we pass blame to the parents. They form a linked list in the
+ * scoreboard structure, sorted by the target line number.
+ */
struct blame_entry {
struct blame_entry *prev;
struct blame_entry *next;
@@ -134,19 +147,24 @@ struct blame_entry {
int s_lno;
/* how significant this entry is -- cached to avoid
- * scanning the lines over and over
+ * scanning the lines over and over.
*/
unsigned score;
};
+/*
+ * The current state of the blame assignment.
+ */
struct scoreboard {
/* the final commit (i.e. where we started digging from) */
struct commit *final;
const char *path;
- /* the contents in the final; pointed into by buf pointers of
- * blame_entries
+ /*
+ * The contents in the final image.
+ * Used by many functions to obtain contents of the nth line,
+ * indexed with scoreboard.lineno[blame_entry.lno].
*/
const char *final_buf;
unsigned long final_buf_size;
@@ -171,6 +189,11 @@ static int cmp_suspect(struct origin *a, struct origin *b)
static void sanity_check_refcnt(struct scoreboard *);
+/*
+ * If two blame entries that are next to each other came from
+ * contiguous lines in the same origin (i.e. <commit, path> pair),
+ * merge them together.
+ */
static void coalesce(struct scoreboard *sb)
{
struct blame_entry *ent, *next;
@@ -194,6 +217,12 @@ static void coalesce(struct scoreboard *sb)
sanity_check_refcnt(sb);
}
+/*
+ * Given a commit and a path in it, create a new origin structure.
+ * The callers that add blame to the scoreboard should use
+ * get_origin() to obtain shared, refcounted copy instead of calling
+ * this function directly.
+ */
static struct origin *make_origin(struct commit *commit, const char *path)
{
struct origin *o;
@@ -204,6 +233,9 @@ static struct origin *make_origin(struct commit *commit, const char *path)
return o;
}
+/*
+ * Locate an existing origin or create a new one.
+ */
static struct origin *get_origin(struct scoreboard *sb,
struct commit *commit,
const char *path)
@@ -218,6 +250,13 @@ static struct origin *get_origin(struct scoreboard *sb,
return make_origin(commit, path);
}
+/*
+ * Fill the blob_sha1 field of an origin if it hasn't, so that later
+ * call to fill_origin_blob() can use it to locate the data. blob_sha1
+ * for an origin is also used to pass the blame for the entire file to
+ * the parent to detect the case where a child's blob is identical to
+ * that of its parent's.
+ */
static int fill_blob_sha1(struct origin *origin)
{
unsigned mode;
@@ -238,6 +277,10 @@ static int fill_blob_sha1(struct origin *origin)
return -1;
}
+/*
+ * We have an origin -- check if the same path exists in the
+ * parent and return an origin structure to represent it.
+ */
static struct origin *find_origin(struct scoreboard *sb,
struct commit *parent,
struct origin *origin)
@@ -247,12 +290,26 @@ static struct origin *find_origin(struct scoreboard *sb,
const char *paths[2];
if (parent->util) {
- /* This is a freestanding copy of origin and not
- * refcounted.
+ /*
+ * Each commit object can cache one origin in that
+ * commit. This is a freestanding copy of origin and
+ * not refcounted.
*/
struct origin *cached = parent->util;
if (!strcmp(cached->path, origin->path)) {
+ /*
+ * The same path between origin and its parent
+ * without renaming -- the most common case.
+ */
porigin = get_origin(sb, parent, cached->path);
+
+ /*
+ * If the origin was newly created (i.e. get_origin
+ * would call make_origin if none is found in the
+ * scoreboard), it does not know the blob_sha1,
+ * so copy it. Otherwise porigin was in the
+ * scoreboard and already knows blob_sha1.
+ */
if (porigin->refcnt == 1)
hashcpy(porigin->blob_sha1, cached->blob_sha1);
return porigin;
@@ -309,7 +366,13 @@ static struct origin *find_origin(struct scoreboard *sb,
}
diff_flush(&diff_opts);
if (porigin) {
+ /*
+ * Create a freestanding copy that is not part of
+ * the refcounted origin found in the scoreboard, and
+ * cache it in the commit.
+ */
struct origin *cached;
+
cached = make_origin(porigin->commit, porigin->path);
hashcpy(cached->blob_sha1, porigin->blob_sha1);
parent->util = cached;
@@ -317,6 +380,10 @@ static struct origin *find_origin(struct scoreboard *sb,
return porigin;
}
+/*
+ * We have an origin -- find the path that corresponds to it in its
+ * parent and return an origin structure to represent it.
+ */
static struct origin *find_rename(struct scoreboard *sb,
struct commit *parent,
struct origin *origin)
@@ -353,6 +420,9 @@ static struct origin *find_rename(struct scoreboard *sb,
return porigin;
}
+/*
+ * Parsing of patch chunks...
+ */
struct chunk {
/* line number in postimage; up to but not including this
* line is the same as preimage
@@ -454,6 +524,11 @@ static struct patch *compare_buffer(mmfile_t *file_p, mmfile_t *file_o,
return state.ret;
}
+/*
+ * Run diff between two origins and grab the patch output, so that
+ * we can pass blame for lines origin is currently suspected for
+ * to its parent.
+ */
static struct patch *get_patch(struct origin *parent, struct origin *origin)
{
mmfile_t file_p, file_o;
@@ -474,6 +549,10 @@ static void free_patch(struct patch *p)
free(p);
}
+/*
+ * Link in a new blame entry to the scorebord. Entries that cover the
+ * same line range have been removed from the scoreboard previously.
+ */
static void add_blame_entry(struct scoreboard *sb, struct blame_entry *e)
{
struct blame_entry *ent, *prev = NULL;
@@ -497,6 +576,12 @@ static void add_blame_entry(struct scoreboard *sb, struct blame_entry *e)
e->next->prev = e;
}
+/*
+ * src typically is on-stack; we want to copy the information in it to
+ * an malloced blame_entry that is already on the linked list of the
+ * scoreboard. The origin of dst loses a refcnt while the origin of src
+ * gains one.
+ */
static void dup_entry(struct blame_entry *dst, struct blame_entry *src)
{
struct blame_entry *p, *n;
@@ -516,25 +601,25 @@ static const char *nth_line(struct scoreboard *sb, int lno)
return sb->final_buf + sb->lineno[lno];
}
+/*
+ * It is known that lines between tlno to same came from parent, and e
+ * has an overlap with that range. it also is known that parent's
+ * line plno corresponds to e's line tlno.
+ *
+ * <---- e ----->
+ * <------>
+ * <------------>
+ * <------------>
+ * <------------------>
+ *
+ * Split e into potentially three parts; before this chunk, the chunk
+ * to be blamed for the parent, and after that portion.
+ */
static void split_overlap(struct blame_entry *split,
struct blame_entry *e,
int tlno, int plno, int same,
struct origin *parent)
{
- /* it is known that lines between tlno to same came from
- * parent, and e has an overlap with that range. it also is
- * known that parent's line plno corresponds to e's line tlno.
- *
- * <---- e ----->
- * <------>
- * <------------>
- * <------------>
- * <------------------>
- *
- * Potentially we need to split e into three parts; before
- * this chunk, the chunk to be blamed for parent, and after
- * that portion.
- */
int chunk_end_lno;
memset(split, 0, sizeof(struct blame_entry [3]));
@@ -564,11 +649,20 @@ static void split_overlap(struct blame_entry *split,
chunk_end_lno = e->lno + e->num_lines;
split[1].num_lines = chunk_end_lno - split[1].lno;
+ /*
+ * if it turns out there is nothing to blame the parent for,
+ * forget about the splitting. !split[1].suspect signals this.
+ */
if (split[1].num_lines < 1)
return;
split[1].suspect = origin_incref(parent);
}
+/*
+ * split_overlap() divided an existing blame e into up to three parts
+ * in split. Adjust the linked list of blames in the scoreboard to
+ * reflect the split.
+ */
static void split_blame(struct scoreboard *sb,
struct blame_entry *split,
struct blame_entry *e)
@@ -576,21 +670,27 @@ static void split_blame(struct scoreboard *sb,
struct blame_entry *new_entry;
if (split[0].suspect && split[2].suspect) {
- /* we need to split e into two and add another for parent */
+ /* The first part (reuse storage for the existing entry e) */
dup_entry(e, &split[0]);
+ /* The last part -- me */
new_entry = xmalloc(sizeof(*new_entry));
memcpy(new_entry, &(split[2]), sizeof(struct blame_entry));
add_blame_entry(sb, new_entry);
+ /* ... and the middle part -- parent */
new_entry = xmalloc(sizeof(*new_entry));
memcpy(new_entry, &(split[1]), sizeof(struct blame_entry));
add_blame_entry(sb, new_entry);
}
else if (!split[0].suspect && !split[2].suspect)
- /* parent covers the entire area */
+ /*
+ * The parent covers the entire area; reuse storage for
+ * e and replace it with the parent.
+ */
dup_entry(e, &split[1]);
else if (split[0].suspect) {
+ /* me and then parent */
dup_entry(e, &split[0]);
new_entry = xmalloc(sizeof(*new_entry));
@@ -598,6 +698,7 @@ static void split_blame(struct scoreboard *sb,
add_blame_entry(sb, new_entry);
}
else {
+ /* parent and then me */
dup_entry(e, &split[1]);
new_entry = xmalloc(sizeof(*new_entry));
@@ -628,6 +729,10 @@ static void split_blame(struct scoreboard *sb,
}
}
+/*
+ * After splitting the blame, the origins used by the
+ * on-stack blame_entry should lose one refcnt each.
+ */
static void decref_split(struct blame_entry *split)
{
int i;
@@ -636,6 +741,10 @@ static void decref_split(struct blame_entry *split)
origin_decref(split[i].suspect);
}
+/*
+ * Helper for blame_chunk(). blame_entry e is known to overlap with
+ * the patch hunk; split it and pass blame to the parent.
+ */
static void blame_overlap(struct scoreboard *sb, struct blame_entry *e,
int tlno, int plno, int same,
struct origin *parent)
@@ -648,6 +757,9 @@ static void blame_overlap(struct scoreboard *sb, struct blame_entry *e,
decref_split(split);
}
+/*
+ * Find the line number of the last line the target is suspected for.
+ */
static int find_last_in_target(struct scoreboard *sb, struct origin *target)
{
struct blame_entry *e;
@@ -662,6 +774,11 @@ static int find_last_in_target(struct scoreboard *sb, struct origin *target)
return last_in_target;
}
+/*
+ * Process one hunk from the patch between the current suspect for
+ * blame_entry e and its parent. Find and split the overlap, and
+ * pass blame to the overlapping part to the parent.
+ */
static void blame_chunk(struct scoreboard *sb,
int tlno, int plno, int same,
struct origin *target, struct origin *parent)
@@ -678,6 +795,11 @@ static void blame_chunk(struct scoreboard *sb,
}
}
+/*
+ * We are looking at the origin 'target' and aiming to pass blame
+ * for the lines it is suspected to its parent. Run diff to find
+ * which lines came from parent and pass blame for them.
+ */
static int pass_blame_to_parent(struct scoreboard *sb,
struct origin *target,
struct origin *parent)
@@ -698,13 +820,22 @@ static int pass_blame_to_parent(struct scoreboard *sb,
plno = chunk->p_next;
tlno = chunk->t_next;
}
- /* rest (i.e. anything above tlno) are the same as parent */
+ /* The rest (i.e. anything after tlno) are the same as the parent */
blame_chunk(sb, tlno, plno, last_in_target, target, parent);
free_patch(patch);
return 0;
}
+/*
+ * The lines in blame_entry after splitting blames many times can become
+ * very small and trivial, and at some point it becomes pointless to
+ * blame the parents. E.g. "\t\t}\n\t}\n\n" appears everywhere in any
+ * ordinary C program, and it is not worth to say it was copied from
+ * totally unrelated file in the parent.
+ *
+ * Compute how trivial the lines in the blame_entry are.
+ */
static unsigned ent_score(struct scoreboard *sb, struct blame_entry *e)
{
unsigned score;
@@ -726,6 +857,12 @@ static unsigned ent_score(struct scoreboard *sb, struct blame_entry *e)
return score;
}
+/*
+ * best_so_far[] and this[] are both a split of an existing blame_entry
+ * that passes blame to the parent. Maintain best_so_far the best split
+ * so far, by comparing this and best_so_far and copying this into
+ * bst_so_far as needed.
+ */
static void copy_split_if_better(struct scoreboard *sb,
struct blame_entry *best_so_far,
struct blame_entry *this)
@@ -745,6 +882,11 @@ static void copy_split_if_better(struct scoreboard *sb,
memcpy(best_so_far, this, sizeof(struct blame_entry [3]));
}
+/*
+ * Find the lines from parent that are the same as ent so that
+ * we can pass blames to it. file_p has the blob contents for
+ * the parent.
+ */
static void find_copy_in_blob(struct scoreboard *sb,
struct blame_entry *ent,
struct origin *parent,
@@ -757,6 +899,9 @@ static void find_copy_in_blob(struct scoreboard *sb,
struct patch *patch;
int i, plno, tlno;
+ /*
+ * Prepare mmfile that contains only the lines in ent.
+ */
cp = nth_line(sb, ent->lno);
file_o.ptr = (char*) cp;
cnt = ent->num_lines;
@@ -792,6 +937,10 @@ static void find_copy_in_blob(struct scoreboard *sb,
free_patch(patch);
}
+/*
+ * See if lines currently target is suspected for can be attributed to
+ * parent.
+ */
static int find_move_in_parent(struct scoreboard *sb,
struct origin *target,
struct origin *parent)
@@ -826,12 +975,15 @@ static int find_move_in_parent(struct scoreboard *sb,
return 0;
}
-
struct blame_list {
struct blame_entry *ent;
struct blame_entry split[3];
};
+/*
+ * Count the number of entries the target is suspected for,
+ * and prepare a list of entry and the best split.
+ */
static struct blame_list *setup_blame_list(struct scoreboard *sb,
struct origin *target,
int *num_ents_p)
@@ -840,9 +992,6 @@ static struct blame_list *setup_blame_list(struct scoreboard *sb,
int num_ents, i;
struct blame_list *blame_list = NULL;
- /* Count the number of entries the target is suspected for,
- * and prepare a list of entry and the best split.
- */
for (e = sb->ent, num_ents = 0; e; e = e->next)
if (!e->guilty && !cmp_suspect(e->suspect, target))
num_ents++;
@@ -856,6 +1005,11 @@ static struct blame_list *setup_blame_list(struct scoreboard *sb,
return blame_list;
}
+/*
+ * For lines target is suspected for, see if we can find code movement
+ * across file boundary from the parent commit. porigin is the path
+ * in the parent we already tried.
+ */
static int find_copy_in_parent(struct scoreboard *sb,
struct origin *target,
struct commit *parent,
@@ -956,7 +1110,8 @@ static int find_copy_in_parent(struct scoreboard *sb,
return retval;
}
-/* The blobs of origin and porigin exactly match, so everything
+/*
+ * The blobs of origin and porigin exactly match, so everything
* origin is suspected for can be blamed on the parent.
*/
static void pass_whole_blame(struct scoreboard *sb,
@@ -1041,7 +1196,7 @@ static void pass_blame(struct scoreboard *sb, struct origin *origin, int opt)
}
/*
- * Optionally run "miff" to find moves in parents' files here.
+ * Optionally find moves in parents' files.
*/
if (opt & PICKAXE_BLAME_MOVE)
for (i = 0, parent = commit->parents;
@@ -1055,7 +1210,7 @@ static void pass_blame(struct scoreboard *sb, struct origin *origin, int opt)
}
/*
- * Optionally run "ciff" to find copies from parents' files here.
+ * Optionally find copies from parents' files.
*/
if (opt & PICKAXE_BLAME_COPY)
for (i = 0, parent = commit->parents;
@@ -1072,6 +1227,9 @@ static void pass_blame(struct scoreboard *sb, struct origin *origin, int opt)
origin_decref(parent_origin[i]);
}
+/*
+ * Information on commits, used for output.
+ */
struct commit_info
{
char *author;
@@ -1088,6 +1246,9 @@ struct commit_info
char *summary;
};
+/*
+ * Parse author/committer line in the commit object buffer
+ */
static void get_ac_line(const char *inbuf, const char *what,
int bufsz, char *person, char **mail,
unsigned long *time, char **tz)
@@ -1142,7 +1303,8 @@ static void get_commit_info(struct commit *commit,
static char committer_buf[1024];
static char summary_buf[1024];
- /* We've operated without save_commit_buffer, so
+ /*
+ * We've operated without save_commit_buffer, so
* we now need to populate them for output.
*/
if (!commit->buffer) {
@@ -1182,6 +1344,10 @@ static void get_commit_info(struct commit *commit,
summary_buf[len] = 0;
}
+/*
+ * To allow LF and other nonportable characters in pathnames,
+ * they are c-style quoted as needed.
+ */
static void write_filename_info(const char *path)
{
printf("filename ");
@@ -1189,6 +1355,10 @@ static void write_filename_info(const char *path)
putchar('\n');
}
+/*
+ * The blame_entry is found to be guilty for the range. Mark it
+ * as such, and show it in incremental output.
+ */
static void found_guilty_entry(struct blame_entry *ent)
{
if (ent->guilty)
@@ -1220,6 +1390,11 @@ static void found_guilty_entry(struct blame_entry *ent)
}
}
+/*
+ * The main loop -- while the scoreboard has lines whose true origin
+ * is still unknown, pick one brame_entry, and allow its current
+ * suspect to pass blames to its parents.
+ */
static void assign_blame(struct scoreboard *sb, struct rev_info *revs, int opt)
{
while (1) {
@@ -1234,12 +1409,16 @@ static void assign_blame(struct scoreboard *sb, struct rev_info *revs, int opt)
if (!suspect)
return; /* all done */
+ /*
+ * We will use this suspect later in the loop,
+ * so hold onto it in the meantime.
+ */
origin_incref(suspect);
commit = suspect->commit;
if (!commit->object.parsed)
parse_commit(commit);
if (!(commit->object.flags & UNINTERESTING) &&
- !(revs->max_age != -1 && commit->date < revs->max_age))
+ !(revs->max_age != -1 && commit->date < revs->max_age))
pass_blame(sb, suspect, opt);
else {
commit->object.flags |= UNINTERESTING;
@@ -1431,6 +1610,10 @@ static void output(struct scoreboard *sb, int option)
}
}
+/*
+ * To allow quick access to the contents of nth line in the
+ * final image, prepare an index in the scoreboard.
+ */
static int prepare_lines(struct scoreboard *sb)
{
const char *buf = sb->final_buf;
@@ -1458,6 +1641,11 @@ static int prepare_lines(struct scoreboard *sb)
return sb->num_lines;
}
+/*
+ * Add phony grafts for use with -S; this is primarily to
+ * support git-cvsserver that wants to give a linear history
+ * to its clients.
+ */
static int read_ancestry(const char *graft_file)
{
FILE *fp = fopen(graft_file, "r");
@@ -1475,6 +1663,9 @@ static int read_ancestry(const char *graft_file)
return 0;
}
+/*
+ * How many columns do we need to show line numbers in decimal?
+ */
static int lineno_width(int lines)
{
int i, width;
@@ -1484,6 +1675,10 @@ static int lineno_width(int lines)
return width;
}
+/*
+ * How many columns do we need to show line numbers, authors,
+ * and filenames?
+ */
static void find_alignment(struct scoreboard *sb, int *option)
{
int longest_src_lines = 0;
@@ -1522,6 +1717,10 @@ static void find_alignment(struct scoreboard *sb, int *option)
max_score_digits = lineno_width(largest_score);
}
+/*
+ * For debugging -- origin is refcounted, and this asserts that
+ * we do not underflow.
+ */
static void sanity_check_refcnt(struct scoreboard *sb)
{
int baa = 0;
@@ -1543,8 +1742,9 @@ static void sanity_check_refcnt(struct scoreboard *sb)
ent->suspect->refcnt = -ent->suspect->refcnt;
}
for (ent = sb->ent; ent; ent = ent->next) {
- /* then pick each and see if they have the the correct
- * refcnt.
+ /*
+ * ... then pick each and see if they have the the
+ * correct refcnt.
*/
int found;
struct blame_entry *e;
@@ -1574,6 +1774,10 @@ static void sanity_check_refcnt(struct scoreboard *sb)
}
}
+/*
+ * Used for the command line parsing; check if the path exists
+ * in the working tree.
+ */
static int has_path_in_work_tree(const char *path)
{
struct stat st;
@@ -1596,6 +1800,9 @@ static const char *add_prefix(const char *prefix, const char *path)
return prefix_path(prefix, strlen(prefix), path);
}
+/*
+ * Parsing of (comma separated) one item in the -L option
+ */
static const char *parse_loc(const char *spec,
struct scoreboard *sb, long lno,
long begin, long *ret)
@@ -1670,6 +1877,9 @@ static const char *parse_loc(const char *spec,
}
}
+/*
+ * Parsing of -L option
+ */
static void prepare_blame_range(struct scoreboard *sb,
const char *bottomtop,
long lno,
@@ -1788,7 +1998,8 @@ int cmd_blame(int argc, const char **argv, const char *prefix)
if (!blame_copy_score)
blame_copy_score = BLAME_DEFAULT_COPY_SCORE;
- /* We have collected options unknown to us in argv[1..unk]
+ /*
+ * We have collected options unknown to us in argv[1..unk]
* which are to be passed to revision machinery if we are
* going to do the "bottom" procesing.
*
@@ -1868,7 +2079,8 @@ int cmd_blame(int argc, const char **argv, const char *prefix)
if (final_commit_name)
argv[unk++] = final_commit_name;
- /* Now we got rev and path. We do not want the path pruning
+ /*
+ * Now we got rev and path. We do not want the path pruning
* but we may want "bottom" processing.
*/
argv[unk++] = "--"; /* terminate the rev name */
@@ -1878,7 +2090,8 @@ int cmd_blame(int argc, const char **argv, const char *prefix)
setup_revisions(unk, argv, &revs, "HEAD");
memset(&sb, 0, sizeof(sb));
- /* There must be one and only one positive commit in the
+ /*
+ * There must be one and only one positive commit in the
* revs->pending array.
*/
for (i = 0; i < revs.pending.nr; i++) {
@@ -1899,7 +2112,10 @@ int cmd_blame(int argc, const char **argv, const char *prefix)
}
if (!sb.final) {
- /* "--not A B -- path" without anything positive */
+ /*
+ * "--not A B -- path" without anything positive;
+ * default to HEAD.
+ */
unsigned char head_sha1[20];
final_commit_name = "HEAD";
@@ -1909,7 +2125,8 @@ int cmd_blame(int argc, const char **argv, const char *prefix)
add_pending_object(&revs, &(sb.final->object), "HEAD");
}
- /* If we have bottom, this will mark the ancestors of the
+ /*
+ * If we have bottom, this will mark the ancestors of the
* bottom commits we would reach while traversing as
* uninteresting.
*/