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Revision 24ff4d56cf400126aa93ac9a5b9d8a21afadf3f6 authored by Björn Gustavsson on 06 March 2010, 14:30:29 UTC, committed by Junio C Hamano on 07 March 2010, 07:53:00 UTC 
apply: Remove the quick rejection test
 
In the next commit, we will make it possible for blank context
lines to match beyond the end of the file. That means that a hunk
with a preimage that has more lines than present in the file may
be possible to successfully apply. Therefore, we must remove
the quick rejection test in find_pos().

find_pos() will already work correctly without the quick
rejection test, but that might not be obvious. Therefore,
comment the test for handling out-of-range line numbers in
find_pos() and cast the "line" variable to the same (unsigned)
type as img->nr.

What are performance implications of removing the quick
rejection test?

It can only help "git apply" to reject a patch faster. For example,
if I have a file with one million lines and a patch that removes
slightly more than 50 percent of the lines and try to apply that
patch twice, the second attempt will fail slightly faster
with the test than without (based on actual measurements).

However, there is the pathological case of a patch with many
more context lines than the default three, and applying that patch
using "git apply -C1". Without the rejection test, the running
time will be roughly proportional to the number of context lines
times the size of the file. That could be handled by writing
a more complicated rejection test (it would have to count the
number of blanks at the end of the preimage), but I don't find
that worth doing until there is a real-world use case that
would benfit from it.

It would be possible to keep the quick rejection test if
--whitespace=fix is not given, but I don't like that from
a testing point of view.

Signed-off-by: Björn Gustavsson <bgustavsson@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
1 parent 9b25949
Raw File
graph.h 
#ifndef GRAPH_H
#define GRAPH_H

/* A graph is a pointer to this opaque structure */
struct git_graph;

/*
 * Create a new struct git_graph.
 */
struct git_graph *graph_init(struct rev_info *opt);

/*
 * Update a git_graph with a new commit.
 * This will cause the graph to begin outputting lines for the new commit
 * the next time graph_next_line() is called.
 *
 * If graph_update() is called before graph_is_commit_finished() returns 1,
 * the next call to graph_next_line() will output an ellipsis ("...")
 * to indicate that a portion of the graph is missing.
 */
void graph_update(struct git_graph *graph, struct commit *commit);

/*
 * Determine if a graph has finished outputting lines for the current
 * commit.
 *
 * Returns 1 if graph_next_line() needs to be called again before
 * graph_update() should be called.  Returns 0 if no more lines are needed
 * for this commit.  If 0 is returned, graph_next_line() may still be
 * called without calling graph_update(), and it will merely output
 * appropriate "vertical padding" in the graph.
 */
int graph_is_commit_finished(struct git_graph const *graph);


/*
 * graph_show_*: helper functions for printing to stdout
 */


/*
 * If the graph is non-NULL, print the history graph to stdout,
 * up to and including the line containing this commit.
 * Does not print a terminating newline on the last line.
 */
void graph_show_commit(struct git_graph *graph);

/*
 * If the graph is non-NULL, print one line of the history graph to stdout.
 * Does not print a terminating newline on the last line.
 */
void graph_show_oneline(struct git_graph *graph);

/*
 * If the graph is non-NULL, print one line of vertical graph padding to
 * stdout.  Does not print a terminating newline on the last line.
 */
void graph_show_padding(struct git_graph *graph);

/*
 * If the graph is non-NULL, print the rest of the history graph for this
 * commit to stdout.  Does not print a terminating newline on the last line.
 */
int graph_show_remainder(struct git_graph *graph);

/*
 * Print a commit message strbuf and the remainder of the graph to stdout.
 *
 * This is similar to graph_show_strbuf(), but it always prints the
 * remainder of the graph.
 *
 * If the strbuf ends with a newline, the output printed by
 * graph_show_commit_msg() will end with a newline.  If the strbuf is
 * missing a terminating newline (including if it is empty), the output
 * printed by graph_show_commit_msg() will also be missing a terminating
 * newline.
 */
void graph_show_commit_msg(struct git_graph *graph, struct strbuf const *sb);

#endif /* GRAPH_H */
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