It's not at all clear to me what happens when you run flutter analyze foo where foo is a path.

In particular:

• if the path is invalid we seem to just ignore it
• consider the differences here, where temp contains a single .dart file, and dev is the directory that contains my flutter checkout dart sdk checkout, engine checkout, etc:

$ cd ~/temp
$ flutter analyze ../dev
Analyzing ../dev...
No analyzer warnings! (ran in 0.2s)
$ cd ~/dev
$ flutter analyze ../dev
Analyzing ....
No analyzer warnings! (ran in 0.2s)
$ flutter analyze
Analyzing 31030 files...

See also #4387 which may be contributing to the confusion.