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This fix resolves the previously-added test_expect_failure in
t4215-log-skewed-merges.sh.
The issue lies in the "else" condition while updating the mapping
inside graph_output_collapsing_line(). In 0f0f389f (graph: tidy up
display of left-skewed merges, 2019-10-15), the output of left-
skewed merges was changed to allow an immediate horizontal edge in
the first parent, output by graph_output_post_merge_line() instead
of by graph_output_collapsing_line(). This condensed the first line
behavior as follows:
Before 0f0f389f:
| | | | | | *-.
| | | | | | |\ \
| |_|_|_|_|/ | |
|/| | | | | / /
After 0f0f389f:
| | | | | | *
| |_|_|_|_|/|\
|/| | | | |/ /
| | | | |/| /
However, a very subtle issue arose when the second and third parent
edges are collapsed in later steps. The second parent edge is now
immediately adjacent to a vertical edge. This means that the
condition
} else if (graph->mapping[i - 1] < 0) {
in graph_output_collapsing_line() evaluates as false. The block for
this condition was the only place where we connected the target
column with the current position with horizontal edge markers.
In this case, the final "else" block is run, and the edge is marked
as horizontal, but did not back-fill the blank columns between the
target and the current edge. Since the second parent edge is marked
as horizontal, the third parent edge is not marked as horizontal.
This causes the output to continue as follows:
Before this change:
| | | | | | *
| |_|_|_|_|/|\
|/| | | | |/ /
| | | | |/| /
| | | |/| |/
| | |/| |/|
| |/| |/| |
| | |/| | |
By adding the logic for "filling" a horizontal edge between the
target column and the current column, we are able to resolve the
issue.
After this change:
| | | | | | *
| |_|_|_|_|/|\
|/| | | | |/ /
| | |_|_|/| /
| |/| | | |/
| | | |_|/|
| | |/| | |
This output properly matches the expected blend of the edge
behavior before 0f0f389f and the merge commit rendering from
0f0f389f.
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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A previous test in t4215-log-skewed-merges.sh was added to demonstrate
exactly the topology of a reported failure in "git log --graph". While
investigating the fix, we realized that multiple edges that could
collapse with horizontal lines were not doing so.
Specifically, examine this section of the graph:
| | | | | | *
| |_|_|_|_|/|\
|/| | | | |/ /
| | | | |/| /
| | | |/| |/
| | |/| |/|
| |/| |/| |
| | |/| | |
| | * | | |
Document this behavior with a test. This behavior is new, as the
behavior in v2.24.1 has the following output:
| | | | | | *-.
| | | | | | |\ \
| |_|_|_|_|/ / /
|/| | | | | / /
| | |_|_|_|/ /
| |/| | | | /
| | | |_|_|/
| | |/| | |
| | * | | |
The behavior changed logically in 479db18b ("graph: smooth appearance
of collapsing edges on commit lines", 2019-10-15), but was actually
broken due to an assert() bug in 458152cc ("graph: example of graph
output that can be simplified", 2019-10-15). A future change could
modify this behavior to do the following instead:
| | | | | | *
| |_|_|_|_|/|\
|/| | | | |/ /
| | |_|_|/| /
| |/| | | |/
| | | |_|/|
| | |/| | |
| | * | | |
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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In some cases, horizontal lines in rendered graphs can lose their
coloring. This is due to a use of graph_line_addch() instead of
graph_line_write_column(). Using a ternary operator to pick the
character is nice for compact code, but we actually need a column to
provide the color.
Add a test to t4215-log-skewed-merges.sh to prevent regression.
Reported-by: Jeff King <peff@peff.net>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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When "git log --graph" shows a merge commit that has two collapsing
lines, like:
| | | | *
| |_|_|/|
|/| | |/
| | |/|
| |/| |
| * | |
* | | |
we trigger an assert():
graph.c:1228: graph_output_collapsing_line: Assertion
`graph->mapping[i - 3] == target' failed.
The assert was introduced by eaf158f8 ("graph API: Use horizontal
lines for more compact graphs", 2009-04-21), which is quite old.
This assert is trying to say that when we complete a horizontal
line with a single slash, it is because we have reached our target.
It is actually the _second_ collapsing line that hits this assert.
The reason we are in this code path is because we are collapsing
the first line, and in that case we are hitting our target now
that the horizontal line is complete. However, the second line
cannot be a horizontal line, so it will collapse without horizontal
lines. In this case, it is inappropriate to assert that we have
reached our target, as we need to continue for another column
before reaching the target. Dropping the assert is safe here.
The new behavior in 0f0f389f12 (graph: tidy up display of
left-skewed merges, 2019-10-15) caused the behavior change that
made this assertion failure possible. In addition to making the
assert possible, it also changed how multiple edges collapse.
In a larger example, the current code will output a collapse
as follows:
| | | | | | *
| |_|_|_|_|/|\
|/| | | | |/ /
| | | | |/| /
| | | |/| |/
| | |/| |/|
| |/| |/| |
| | |/| | |
| | * | | |
However, the intended collapse should allow multiple horizontal lines
as follows:
| | | | | | *
| |_|_|_|_|/|\
|/| | | | |/ /
| | |_|_|/| /
| |/| | | |/
| | | |_|/|
| | |/| | |
| | * | | |
This behavior is not corrected by this change, but is noted for a later
update.
Helped-by: Jeff King <peff@peff.net>
Reported-by: Bradley Smith <brad@brad-smith.co.uk>
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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When git commands are placed in the upstream of a pipe, their return
codes are lost. In this particular case, it is especially bad since we
are testing the intricacies of `git log --graph` behavior and if we hit
an unexpected failure or segfault, we want to know this.
Extract the common output checking logic into check_graph() where we
redirect the output of git commands upstream of pipe into a file and
have sed read from that file so that git failures are detected.
This patch is best viewed with `--color-moved`.
Signed-off-by: Denton Liu <liu.denton@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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When a merge commit is printed and its final parent is the same commit
that occupies the column to the right of the merge, this results in a
kink in the displayed edges:
* |
|\ \
| |/
| *
Graphs containing these shapes can be hard to read, as the expansion to
the right followed immediately by collapsing back to the left creates a
lot of zig-zagging edges, especially when many columns are present.
We can improve this by eliminating the zig-zag and having the merge's
final parent edge fuse immediately with its neighbor:
* |
|\|
| *
This reduces the horizontal width for the current commit by 2, and
requires one less row, making the graph display more compact. Taken in
combination with other graph-smoothing enhancements, it greatly
compresses the space needed to display certain histories:
*
|\
| * *
| |\ |\
| | * | *
| | | | |\
| | \ | | *
| *-. \ | * |
| |\ \ \ => |/|\|
|/ / / / | | *
| | | / | * |
| | |/ | |/
| | * * /
| * | |/
| |/ *
* |
|/
*
One of the test cases here cannot be correctly rendered in Git v2.23.0;
it produces this output following commit E:
| | *-. \ 5_E
| | |\ \ \
| |/ / / /
| | | / _
| |_|/
|/| |
The new implementation makes sure that the rightmost edge in this
history is not left dangling as above.
Signed-off-by: James Coglan <jcoglan@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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When a graph contains edges that are in the process of collapsing to the
left, but those edges cross a commit line, the effect is that the edges
have a jagged appearance:
*
|\
| *
| \
*-. \
|\ \ \
| | * |
| * | |
| |/ /
* | |
|/ /
* |
|/
*
We already takes steps to smooth edges like this when they're expanding;
when an edge appears to the right of a merge commit marker on a
GRAPH_COMMIT line immediately following a GRAPH_POST_MERGE line, we
render it as a `\`:
* \
|\ \
| * \
| |\ \
We can make a similar improvement to collapsing edges, making them
easier to follow and giving the overall graph a feeling of increased
symmetry:
*
|\
| *
| \
*-. \
|\ \ \
| | * |
| * | |
| |/ /
* / /
|/ /
* /
|/
*
To do this, we introduce a new special case for edges on GRAPH_COMMIT
lines that immediately follow a GRAPH_COLLAPSING line. By retaining a
copy of the `mapping` array used to render the GRAPH_COLLAPSING line in
the `old_mapping` array, we can determine that an edge is collapsing
through the GRAPH_COMMIT line and should be smoothed.
Signed-off-by: James Coglan <jcoglan@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Following the introduction of "left-skewed" merges, which are merges
whose first parent fuses with another edge to its left, we have some
more edge cases to deal with in the display of commit and post-merge
lines.
The current graph code handles the following cases for edges appearing
to the right of the commit (*) on commit lines. A 2-way merge is usually
followed by vertical lines:
| | |
| * |
| |\ \
An octopus merge (more than two parents) is always followed by edges
sloping to the right:
| | \ | | \
| *-. \ | *---. \
| |\ \ \ | |\ \ \ \
A 2-way merge is followed by a right-sloping edge if the commit line
immediately follows a post-merge line for a commit that appears in the
same column as the current commit, or any column to the left of that:
| * | * |
| |\ | |\ \
| * \ | | * \
| |\ \ | | |\ \
This commit introduces the following new cases for commit lines. If a
2-way merge skews to the left, then the edges to its right are always
vertical lines, even if the commit follows a post-merge line:
| | | | |\
| * | | * |
|/| | |/| |
A commit with 3 parents that skews left is followed by vertical edges:
| | |
| * |
|/|\ \
If a 3-way left-skewed merge commit appears immediately after a
post-merge line, then it may be followed the right-sloping edges, just
like a 2-way merge that is not skewed.
| |\
| * \
|/|\ \
Octopus merges with 4 or more parents that skew to the left will always
be followed by right-sloping edges, because the existing columns need to
expand around the merge.
| | \
| *-. \
|/|\ \ \
On post-merge lines, usually all edges following the current commit
slope to the right:
| * | |
| |\ \ \
However, if the commit is a left-skewed 2-way merge, the edges to its
right remain vertical. We also need to display a space after the
vertical line descending from the commit marker, whereas this line would
normally be followed by a backslash.
| * | |
|/| | |
If a left-skewed merge has more than 2 parents, then the edges to its
right are still sloped as they bend around the edges introduced by the
merge.
| * | |
|/|\ \ \
To handle these new cases, we need to know not just how many parents
each commit has, but how many new columns it adds to the display; this
quantity is recorded in the `edges_added` field for the current commit,
and `prev_edges_added` field for the previous commit.
Here, "column" refers to visual columns, not the logical columns of the
`columns` array. This is because even if all the commit's parents end up
fusing with existing edges, they initially introduce distinct edges in
the commit and post-merge lines before those edges collapse. For
example, a 3-way merge whose 2nd and 3rd parents fuse with existing
edges still introduces 2 visual columns that affect the display of edges
to their right.
| | | \
| | *-. \
| | |\ \ \
| |_|/ / /
|/| | / /
| | |/ /
| |/| |
| | | |
This merge does not introduce any *logical* columns; there are 4 edges
before and after this commit once all edges have collapsed. But it does
initially introduce 2 new edges that need to be accommodated by the
edges to their right.
Signed-off-by: James Coglan <jcoglan@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Currently, when we display a merge whose first parent is already present
in a column to the left of the merge commit, we display the first parent
as a vertical pipe `|` in the GRAPH_POST_MERGE line and then immediately
enter the GRAPH_COLLAPSING state. The first-parent line tracks to the
left and all the other parent lines follow it; this creates a "kink" in
those lines:
| *---.
| |\ \ \
|/ / / /
| | | *
This change tidies the display of such commits such that if the first
parent appears to the left of the merge, we render it as a `/` and the
second parent as a `|`. This reduces the horizontal and vertical space
needed to render the merge, and makes the resulting lines easier to
read.
| *-.
|/|\ \
| | | *
If the first parent is separated from the merge by several columns, a
horizontal line is drawn in a similar manner to how the GRAPH_COLLAPSING
state displays the line.
| | | *-.
| |_|/|\ \
|/| | | | *
This effect is applied to both "normal" two-parent merges, and to
octopus merges. It also reduces the vertical space needed for pre-commit
lines, as the merge occupies one less column than usual.
Before: After:
| * | *
| |\ | |\
| | \ | * \
| | \ |/|\ \
| *-. \
| |\ \ \
Signed-off-by: James Coglan <jcoglan@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The commits following this one introduce a series of improvements to the
layout of graphs, tidying up a few edge cases, namely:
- merge whose first parent fuses with an existing column to the left
- merge whose last parent fuses with its immediate neighbor on the right
- edges that collapse to the left above and below a commit line
This test case exemplifies these cases and provides a motivating example
of the kind of history I'm aiming to clear up.
The first parent of merge E is the same as the parent of H, so those
edges fuse together.
* H
|
| *-. E
| |\ \
|/ / /
|
* B
We can "skew" the display of this merge so that it doesn't introduce
additional columns that immediately collapse:
* H
|
| * E
|/|\
|
* B
The last parent of E is D, the same as the parent of F which is the edge
to the right of the merge.
* F
|
\
*-. \ E
|\ \ \
/ / / /
| /
|/
* D
The two edges leading to D could be fused sooner: rather than expanding
the F edge around the merge and then letting the edges collapse, the F
edge could fuse with the E edge in the post-merge line:
* F
|
\
*-. | E
|\ \|
/ / /
|
* D
If this is combined with the "skew" effect above, we get a much cleaner
graph display for these edges:
* F
|
* | E
/|\|
|
* D
Finally, the edge leading from C to A appears jagged as it passes
through the commit line for B:
| * | C
| |/
* | B
|/
* A
This can be smoothed out so that such edges are easier to read:
| * | C
| |/
* / B
|/
* A
Signed-off-by: James Coglan <jcoglan@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Derrick Stolee
Denton Liu
James Coglan