Display build metadata on siad startup and via siac version

[tbenz9]

When running your own build it can sometimes be difficult to identify exactly which commit you are running from. This adds additional build information to the siac version command, and displays the git revision hash when siad starts up. If the build was not completed via the Makefile siad will display a warning on start and siac version will not display any of the build information.

[tbenz9]

Sample output of siac version:

Sia Client
        Version 1.3.2
        Git Revision 9a1aab6
        Git Branch build-version
        Build Time 2018-03-07T21:05:59-0800
Sia Daemon
        Version 1.3.2
        Git Revision 9a1aab6
        Git Branch build-version
        Build Time 2018-03-07T21:05:59-0800

Sample output of siad starting:

Sia Daemon v1.3.2
Git Revision 9a1aab6
Loading...
(0/2) Loading siad...
(1/2) Loading gateway...
(2/2) Loading consensus...
Finished loading in 0.221536432 seconds

[ChrisSchinnerl]

I think something like the following might improve the alignment of the left and right block and might make it easier to read.

fmt.Println("\tGit Revision: " + dvg.GitRevision)
fmt.Println("\tGit Branch:   " + dvg.GitBranch)
fmt.Println("\tBuild Time:   " + dvg.BuildTime)

[ChrisSchinnerl]

I don't know if we really need the build time and branch. What do you think @lukechampine ?

[lukechampine]

branch shouldn't be necessary; the commit hash should be sufficient. Build time isn't strictly necessary, but I could imagine it helping in some cases (e.g. "when did we build the last RC?"). The one thing I would change is using the default date command instead of the specially formatted one. date by default outputs a nice human-readable representation of the date.

[tbenz9]

@lukechampine date is formatted that way because make is very weird about what it tries to interpret as arguments. For example this doesn't work:

tbenz9@spartan1:~/go/src/github.com/NebulousLabs/Sia$ make release                                                                                           
go install -tags='netgo' -a -ldflags='-s -w -X github.com/NebulousLabs/Sia/build.GitRevision=✗-e9c221a -X github.com/NebulousLabs/Sia/build.BuildTime="Fri Mar  9 10:05:23 PST 2018"' ./build ./cmd/siac ./cmd/siad ...

But this does:

tbenz9@spartan1:~/go/src/github.com/NebulousLabs/Sia$ make release                                                                                           
go install -tags='netgo' -a -ldflags='-s -w -X github.com/NebulousLabs/Sia/build.GitRevision=✗-e9c221a -X github.com/NebulousLabs/Sia/build.BuildTime="FriMar910:05:23PST2018"' ./build ./cmd/siac ./cmd/siad ...

You would think the "" around date would allow it to be passed in as a string, but that is not working for me. We can either troubleshoot make or come up with a date string without spaces.

[ChrisSchinnerl]

@tbenz9 I don't have lots of experience with that but can you escape the spaces with a \ before the space?

[tbenz9]

@ChrisSchinnerl good idea but didn't work.

tbenz9@spartan1:~/go/src/github.com/NebulousLabs/Sia$ make release                                                                                                                                                                                                                                                            
go install -tags='netgo' -a -ldflags='-s -w -X github.com/NebulousLabs/Sia/build.GitRevision=✗-e9c221a -X github.com/NebulousLabs/Sia/build.BuildTime="Fri\ Mar\ 09\ 11:01:42PST2018"' ./build ./cmd/siac ./cmd/siad

still fails with a 'usage' error meaning the arguments aren't recognized.

[ChrisSchinnerl]

In case anyone else is wondering, we found the issue. The following works:

go install -tags='netgo' -a -ldflags="-s -w -X 'github.com/NebulousLabs/Sia/build.BuildTime=Fri Mar 9 10:05:23 PST 2018'" ./build ./cmd/siac

[lukechampine]

ah yeah, single quotes is the way to go.

You can actually also just enclose the commands in backticks (`); then, when you run the go install command, those commands will be run. e.g.

go install -ldflags="-X 'github.com/NebulousLabs/Sia/build.BuildTime=`date`'" 

but what we have now is fine

[lukechampine]

these will need to be documented, but we can handle that in a separate PR. I want to include this change in the rc

[lukechampine]

looks like golint complains about these:

build/commit.go:5:2: exported var BuildTime should have its own declaration