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path: root/t/t4215-log-skewed-merges.sh
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2020-01-08graph: fix lack of color in horizontal linesLibravatar Derrick Stolee1-0/+29
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>
2020-01-08graph: drop assert() for merge with two collapsing parentsLibravatar Derrick Stolee1-0/+42
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>
2019-11-13t4215: use helper function to check outputLibravatar Denton Liu1-111/+97
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>
2019-10-16graph: flatten edges that fuse with their right neighborLibravatar James Coglan1-9/+47
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>
2019-10-16graph: smooth appearance of collapsing edges on commit linesLibravatar James Coglan1-2/+2
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>
2019-10-16graph: commit and post-merge lines for left-skewed mergesLibravatar James Coglan1-2/+145
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>
2019-10-16graph: tidy up display of left-skewed mergesLibravatar James Coglan1-6/+39
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>
2019-10-16graph: example of graph output that can be simplifiedLibravatar James Coglan1-0/+43
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>