Detect '-o' argument in custom command.

[vitorenesduarte]

Previously, if argument -o was set in the custom command, flamegraph would fail to compute perf's output since it would look for the default perf.data file.

Now, we detect if the user sets perf's output file with -o and build the flamegraph from that file instead.

With this change, the following command now seems to work:

flamegraph -c "record -F 997 --call-graph dwarf -g -o my_perf.data" date
Fri Jul 31 12:02:05 CEST 2020
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.075 MB my_perf.data (7 samples) ]
writing flamegraph to "flamegraph.svg"

Without this change, this is the error we get:

flamegraph -c "record -F 997 --call-graph dwarf -g -o my_perf.data" date
Fri Jul 31 12:03:08 CEST 2020
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.075 MB my_perf.data (7 samples) ]
writing flamegraph to "flamegraph.svg"
thread 'main' panicked at 'unable to generate a flamegraph from the collapsed stack data: Io(Custom { kind: InvalidData, error: "No stack counts found" })', /home/vitor.enes/.cargo/registry/src/github.com-1ecc6299db9ec823/flamegraph-0.3.1/src/lib.rs:273:6
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

[spacejam]

Thanks for this fix! I'll be merging this into a new release in the next few minutes if bors is happy.

bors r+

[bors]

Build succeeded:

• build (ubuntu-latest)
• build (macOS-latest)
• lint
• build (windows-latest)

[spacejam]

Version 0.4 has been released which includes these changes. Thank you :)

[vitorenesduarte]

Awesome, thanks!