Fix self update

[lucklove]

Signed-off-by: lucklove gnu.crazier@gmail.com

What problem does this PR solve?

The code in the master branch will get the tiup binary lost after execution tiup update --self:

This is because we treat tiup as a normal component and install it to ~/.tiup/components/tiup/{version}/ in SelfUpdate and once it's installed SelfUpdate will return nil and the old tiup binary will be remove from ~/.tup/bin.

In a word, it should be installed to "/.tiup/bin" instead of "/.tiup/components/tiup/{version}/"

What is changed and how it works?

Read the TargetDir field of ComponentSpec, if it's not empty, install component to where it's specified.

Check List

Tests

• Integration test

Related changes

• Need to cherry-pick to the release branch

Release notes:

NONE

[codecov-commenter]

Codecov Report

Merging #816 into master will decrease coverage by 0.20%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #816      +/-   ##
==========================================
- Coverage   52.73%   52.52%   -0.21%     
==========================================
  Files         262      262              
  Lines       18965    18971       +6     
==========================================
- Hits        10001     9965      -36     
- Misses       7404     7447      +43     
+ Partials     1560     1559       -1     

Flag	Coverage Δ
#cluster	44.42% <0.00%> (-0.30%)	⬇️
#dm	25.15% <0.00%> (-0.08%)	⬇️
#integrate	47.53% <0.00%> (-0.23%)	⬇️
#playground	22.17% <0.00%> (-0.03%)	⬇️
#tiup	10.83% <0.00%> (-0.01%)	⬇️
#unittest	18.81% <0.00%> (-0.01%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
cmd/update.go	50.00% <0.00%> (ø)
pkg/repository/mirror.go	47.20% <0.00%> (-1.57%)	⬇️
pkg/repository/v1_repository.go	65.05% <0.00%> (-0.34%)	⬇️
pkg/cluster/clusterutil/parse_topology.go	30.00% <0.00%> (-30.00%)	⬇️
pkg/cluster/task/update_meta.go	56.52% <0.00%> (-10.87%)	⬇️
pkg/cluster/operation/scale_in.go	41.66% <0.00%> (-10.42%)	⬇️
pkg/cliutil/cliutil.go	60.71% <0.00%> (-7.15%)	⬇️
pkg/cluster/spec/tispark.go	64.13% <0.00%> (-3.27%)	⬇️
pkg/cluster/api/dmapi.go	56.52% <0.00%> (-1.74%)	⬇️
pkg/cluster/operation/action.go	50.81% <0.00%> (-0.70%)	⬇️
... and 4 more

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[lonng]

lgtm

[lonng]

/merge

[ti-srebot]

Your auto merge job has been accepted, waiting for:

• 817

[ti-srebot]

/run-all-tests

[ti-srebot]

@lucklove merge failed.