Q:

Git merging text files with content including merge conflict syntax

When merging two complete different files, git changes the file to something like below to show that there are conflicts between the files:
<<<<<<< HEAD
[fileA's content]
=======
[fileB's content]
>>>>>>> newbranch

And I'm thinking that if I change the fileA's content with fake syntaxes:
text1
=======
text2
>>>>>>> newbranch
text3
<<<<<<< HEAD
text4

When trying to merge, the conflict file will be like:
<<<<<<< HEAD
text1
=======
text2
>>>>>>> newbranch
text3
<<<<<<< HEAD
text4
=======
[fileB's content]
>>>>>>> newbranch

Question
How does git know which of the syntaxes are real or fake?  Or the content above simply breaks the merging process? 

A:

The output of the file is only for you to view the changes. 
Git doesn't care and does nothing with the content of the file. 
In real life behind the scenes iss saving the delta of the content and generate a full snapshot of the current repository marked with the SHA-1. 
It's a bit more complicated but i tried to explain it as simple as i can. 

The output which you suggested is more similar to diff3 then to diff2. 
For general knowledge here specs for diff2 & diff3. 

diff2: http://www.xmailserver.org/diff2.pdf
diff3: http://www.cis.upenn.edu/~bcpierce/papers/diff3-short.pdf

This is the output of diff3:
cauliflower
<<<<<<< HEAD
peas
potatoes
||||||| merged common ancestors
peas
=======
>>>>>>> topic
tomatoes

How does git know which of the syntaxes are real or fake?  Or the content above simply breaks the merging process? 

Again: 
Git doesn't care about the content.  
Once you merge the content (and you can re-write the whole file) you add it again to git and then git calculate the new diff (regardless of the content, you leave it with all the content added by the merge or change it) and commit it to the repository.