patchgraph.c: visual difference on subsequent series

> For projects with separate history lines and, thus, multiple root-commits, the
> linear arrangement of `git log --graph --oneline` does not allow the user to
> spot where the sequence ends, giving the impression that it's a contiguous
> history. E.g.
>
> History sequence A: a1 -- a2 -- a3 (root-commit)
> History sequence B: b1 -- b2 -- b3 (root-commit)
>
>     git log --graph --oneline
>     * a1
>     * a2
>     * a3
>     * b1
>     * b2
>     * b3
>
> In a GUI tool, the root-commit of each series would stand out on the graph.
>
> This modification changes the commit char to a different symbol ('o'), so users
> of the command-line graph tool can easily identify root-commits and make sense
> of where each series is limited to.
>
>     git log --graph --oneline
>     * a1
>     * a2
>     o a3
>     * b1
>     * b2
>     o b3
>
> The 'o' character was chosen because it is the same character used in rev-list
> to mark root commits.
>
> This patch is similar than the one provided by Milton Soares Filho in
> 1382734287.31768.1.git.send.email.milton.soares.filho@gmail.com but was
> implemented independently and uses the 'o' character instead of 'x'.
>
> Other solutions were discarded for those reasons:
>
>  * line delimiters: we want to keep one commit per line
>  * tree indentation: it makes little sense with commit trees without
>    common history, and is more complicated to implement
>
> Signed-off-by: Antoine Beaupré <anarcat@koumbit.org>
> ---
>  revision.c                                 |  8 ++++++--
>  t/t4202-log.sh                             | 10 +++++-----
>  t/t6016-rev-list-graph-simplify-history.sh | 14 +++++++-------
>  3 files changed, 18 insertions(+), 14 deletions(-)
>
> diff --git a/revision.c b/revision.c
> index 75dda92..5f21e24 100644
> --- a/revision.c
> +++ b/revision.c
> @@ -3246,8 +3246,12 @@ char *get_revision_mark(const struct rev_info *revs, const struct commit *commit
>  			return "<";
>  		else
>  			return ">";
> -	} else if (revs->graph)
> -		return "*";
> +	} else if (revs->graph) {
> +		if (commit->parents)
> +			return "*";
> +		else
> +			return "o";
> +	}
>  	else if (revs->cherry_mark)
>  		return "+";
>  	return "";
> diff --git a/t/t4202-log.sh b/t/t4202-log.sh
> index 99ab7ca..d11876e 100755
> --- a/t/t4202-log.sh
> +++ b/t/t4202-log.sh
> @@ -244,7 +244,7 @@ cat > expect <<EOF
>  * fourth
>  * third
>  * second
> -* initial
> +o initial
>  EOF
>  
>  test_expect_success 'simple log --graph' '
> @@ -272,7 +272,7 @@ cat > expect <<\EOF
>  |/
>  * third
>  * second
> -* initial
> +o initial
>  EOF
>  
>  test_expect_success 'log --graph with merge' '
> @@ -338,7 +338,7 @@ cat > expect <<\EOF
>  |
>  |     second
>  |
> -* commit tags/side-1~3
> +o commit tags/side-1~3
>    Author: A U Thor <author@example.com>
>  
>        initial
> @@ -410,7 +410,7 @@ cat > expect <<\EOF
>  * | third
>  |/
>  * second
> -* initial
> +o initial
>  EOF
>  
>  test_expect_success 'log --graph with merge' '
> @@ -799,7 +799,7 @@ cat >expect <<\EOF
>  | -one
>  | +ichi
>  |
> -* commit COMMIT_OBJECT_NAME
> +o commit COMMIT_OBJECT_NAME
>    Author: A U Thor <author@example.com>
>  
>        initial
> diff --git a/t/t6016-rev-list-graph-simplify-history.sh b/t/t6016-rev-list-graph-simplify-history.sh
> index f7181d1..74b6fc3 100755
> --- a/t/t6016-rev-list-graph-simplify-history.sh
> +++ b/t/t6016-rev-list-graph-simplify-history.sh
> @@ -81,7 +81,7 @@ test_expect_success '--graph --all' '
>  	echo "|/|   " >> expected &&
>  	echo "* | $A2" >> expected &&
>  	echo "|/  " >> expected &&
> -	echo "* $A1" >> expected &&
> +	echo "o $A1" >> expected &&
>  	git rev-list --graph --all > actual &&
>  	test_cmp expected actual
>  	'
> @@ -111,7 +111,7 @@ test_expect_success '--graph --simplify-by-decoration' '
>  	echo "|/|   " >> expected &&
>  	echo "* | $A2" >> expected &&
>  	echo "|/  " >> expected &&
> -	echo "* $A1" >> expected &&
> +	echo "o $A1" >> expected &&
>  	git rev-list --graph --all --simplify-by-decoration > actual &&
>  	test_cmp expected actual
>  	'
> @@ -139,7 +139,7 @@ test_expect_success '--graph --simplify-by-decoration prune branch B' '
>  	echo "* | $A3" >> expected &&
>  	echo "|/  " >> expected &&
>  	echo "* $A2" >> expected &&
> -	echo "* $A1" >> expected &&
> +	echo "o $A1" >> expected &&
>  	git rev-list --graph --simplify-by-decoration --all > actual &&
>  	test_cmp expected actual
>  	'
> @@ -156,7 +156,7 @@ test_expect_success '--graph --full-history -- bar.txt' '
>  	echo "| |/  " >> expected &&
>  	echo "* | $A3" >> expected &&
>  	echo "|/  " >> expected &&
> -	echo "* $A2" >> expected &&
> +	echo "o $A2" >> expected &&
>  	git rev-list --graph --full-history --all -- bar.txt > actual &&
>  	test_cmp expected actual
>  	'
> @@ -170,7 +170,7 @@ test_expect_success '--graph --full-history --simplify-merges -- bar.txt' '
>  	echo "* | $A5" >> expected &&
>  	echo "* | $A3" >> expected &&
>  	echo "|/  " >> expected &&
> -	echo "* $A2" >> expected &&
> +	echo "o $A2" >> expected &&
>  	git rev-list --graph --full-history --simplify-merges --all \
>  		-- bar.txt > actual &&
>  	test_cmp expected actual
> @@ -183,7 +183,7 @@ test_expect_success '--graph -- bar.txt' '
>  	echo "* $A3" >> expected &&
>  	echo "| * $C4" >> expected &&
>  	echo "|/  " >> expected &&
> -	echo "* $A2" >> expected &&
> +	echo "o $A2" >> expected &&
>  	git rev-list --graph --all -- bar.txt > actual &&
>  	test_cmp expected actual
>  	'
> @@ -201,7 +201,7 @@ test_expect_success '--graph --sparse -- bar.txt' '
>  	echo "| * $C1" >> expected &&
>  	echo "|/  " >> expected &&
>  	echo "* $A2" >> expected &&
> -	echo "* $A1" >> expected &&
> +	echo "o $A1" >> expected &&
>  	git rev-list --graph --sparse --all -- bar.txt > actual &&
>  	test_cmp expected actual
>  	'
> -- 
> 2.1.1
>

> Any reason why this patch wasn't included / reviewed?
> ...
>> This patch is similar than the one provided by Milton Soares Filho in
>> 1382734287.31768.1.git.send.email.milton.soares.filho@gmail.com but was
>> implemented independently and uses the 'o' character instead of 'x'.

> Antoine Beaupré <anarcat@koumbit.org> writes:
> 
>> Any reason why this patch wasn't included / reviewed?
>> ...
>>> This patch is similar than the one provided by Milton Soares Filho in
>>> 1382734287.31768.1.git.send.email.milton.soares.filho@gmail.com but was
>>> implemented independently and uses the 'o' character instead of 'x'.
> 
> The reason why Milton's patch was not taken after discussion [*1*]
> was not because its implementation was poor, but its design was not
> good.  By overriding '*' '<' or '>' with x, it made it impossible to
> distinguish a root on the left side branch and a root on the right
> side branch.
> 
> Is the design of your independent implementation the same except
> that 'o' is used instead of 'x'?  Independent implementation does
> not make the same design magically better, if that is the case ;-)

> If the design is different, please explain how your patch solves the
> issue with Milton's design in your log message.
> 
> For example, you could use the column arrangement to solve it, e.g.
> 
> History sequence A: a1 -- a2 -- a3 (root-commit)
> History sequence B: b1 -- b2 -- b3 (root-commit)
> 
>     $ git log --graph --oneline A B
>     * a1
>     * a2
>     * a3
>       * b1
>       * b2
>       * b3
> 
>     $ git log --graph --oneline --left-right A...B
>     < a1
>     < a2
>     < a3
>       > b1
>       > b2
>       > b3
> 
> I am not saying that the above would be the only way to do so; there
> may be other ways to solve the issue.
> 
> [Reference]
> 
> *1* http://thread.gmane.org/gmane.comp.version-control.git/236708/focus=236843
> 

>> Is the design of your independent implementation the same except
>> that 'o' is used instead of 'x'?  Independent implementation does
>> not make the same design magically better, if that is the case ;-)
>
> Interestingly, the patch to the tests lists * to o changes only, no < or
>> to o.

> Michael J Gruber <git@drmicha.warpmail.net> writes:
> 
>>> Is the design of your independent implementation the same except
>>> that 'o' is used instead of 'x'?  Independent implementation does
>>> not make the same design magically better, if that is the case ;-)
>>
>> Interestingly, the patch to the tests lists * to o changes only, no < or
>>> to o.
> 
> Well, in that case, then the opposite but an equivalent problem
> exists in the design, no?  It promises to make roots stand out by
> painting them as 'o', but it sometimes fails to do so.  In other
> words, ...
> 
>> The reason is simply that the patch doesn't change anything for left nor
>> right commits. I would say that is the best compromise since it does not
>> change the overall layout, provides more information by default and does
>> not override information that is requested specifically.
> 
> ... it fails your last criteria.

>> If we want to put more information into log --graph simultaneously we
>> should really go beyond ASCII and look at how tig does it, e.g. using
>> unicode characters.
> 
> That's another way to do so, but shifting columns to show where the
> history is not connected also does not change the overall layout,
> provides more information by default, etc., and a big plus is that
> it would be an approach to do so without having to go beyond ASCII.

>>> If we want to put more information into log --graph simultaneously we
>>> should really go beyond ASCII and look at how tig does it, e.g. using
>>> unicode characters.
>> 
>> That's another way to do so, but shifting columns to show where the
>> history is not connected also does not change the overall layout,
>> provides more information by default, etc., and a big plus is that
>> it would be an approach to do so without having to go beyond ASCII.
>
> That would consume more horizontal space and annoy at least some people.